diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 1137b96..8e165f1 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -17,26 +17,28 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13']
+        python-version: ['3.10', '3.11', '3.12', '3.13', '3.14', '3.15']
 
     steps:
-    - uses: actions/checkout@v3
-    
-    - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v4
+    - uses: actions/checkout@v7.0.1
       with:
+        persist-credentials: false
+
+    - name: Install uv + caching
+      uses: astral-sh/setup-uv@v10.0.0
+      with:
+        enable-cache: true
+        cache-dependency-glob: |
+          setup.*
+          tox.ini
+          pyproject.toml
         python-version: ${{ matrix.python-version }}
 
-    - name: Install depenencies (Ubuntu)
+    - name: Install dependencies (Ubuntu)
       if: runner.os == 'Linux'
       run: |
         sudo apt-get update
         sudo apt-get install -y mercurial subversion
 
-    - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        pip install tox tox-gh-actions
-        
     - name: Test with tox
-      run: tox
+      run: uvx --with tox-uv --with tox-gh-actions tox
diff --git a/CHANGES.rst b/CHANGES.rst
index c732cc7..6976bcd 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -2,10 +2,12 @@ Changelog
 =========
 
 
-2.1.1 (unreleased)
+3.0.0 (unreleased)
 ------------------
 
-- Nothing changed yet.
+- Add support for Python 3.14 and 3.15.  [maurits]
+
+- Require Python 3.10 or higher.  [maurits]
 
 
 2.1.0 (2026-08-20)
diff --git a/MANIFEST.in b/MANIFEST.in
index 4e18b6b..c80f692 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,3 +1,2 @@
 include *.rst
 include *.ini
-prune mr.developer.addon
diff --git a/setup.cfg b/setup.cfg
index 1b713b6..a49c593 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,3 @@
-[bdist_wheel]
-universal = 1
-
 [zest.releaser]
 version-levels = 2
 
diff --git a/setup.py b/setup.py
index 618b344..cf4be76 100644
--- a/setup.py
+++ b/setup.py
@@ -1,13 +1,12 @@
 from setuptools import setup
 
 
-version = '2.1.1.dev0'
+version = '3.0.0.dev0'
 
 
 install_requires = [
     'setuptools',
     'zc.buildout',
-    'six',
 ]
 
 tests_require = [
@@ -33,25 +32,19 @@ def get_text_from_file(fn):
       classifiers=[
           "Development Status :: 5 - Production/Stable",
           "Programming Language :: Python",
-          "Programming Language :: Python :: 2",
-          "Programming Language :: Python :: 2.7",
           "Programming Language :: Python :: 3",
-          "Programming Language :: Python :: 3.4",
-          "Programming Language :: Python :: 3.5",
-          "Programming Language :: Python :: 3.6",
-          "Programming Language :: Python :: 3.7",
-          "Programming Language :: Python :: 3.8",
-          "Programming Language :: Python :: 3.9",
           "Programming Language :: Python :: 3.10",
           "Programming Language :: Python :: 3.11",
           "Programming Language :: Python :: 3.12",
           "Programming Language :: Python :: 3.13",
+          "Programming Language :: Python :: 3.14",
+          "Programming Language :: Python :: 3.15",
           "Framework :: Buildout",
           "Topic :: Software Development :: Libraries :: Python Modules"],
       keywords='buildout extension vcs git develop',
       author='Florian Schulze',
       author_email='florian.schulze@gmx.net',
-      url='http://github.com/fschulze/mr.developer',
+      url='https://github.com/fschulze/mr.developer',
       license='BSD',
       packages=['mr', 'mr.developer', 'mr.developer.tests'],
       package_dir={'': 'src'},
@@ -61,7 +54,7 @@ def get_text_from_file(fn):
       install_requires=install_requires,
       tests_require=tests_require,
       extras_require=extras_require,
-      python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*",
+      python_requires=">=3.10",
       test_suite='mr.developer.tests',
       entry_points="""
       [console_scripts]
diff --git a/src/mr/developer/bazaar.py b/src/mr/developer/bazaar.py
index b0a8542..a3af456 100644
--- a/src/mr/developer/bazaar.py
+++ b/src/mr/developer/bazaar.py
@@ -12,7 +12,7 @@ class BazaarError(common.WCError):
 class BazaarWorkingCopy(common.BaseWorkingCopy):
 
     def __init__(self, source):
-        super(BazaarWorkingCopy, self).__init__(source)
+        super().__init__(source)
         self.bzr_executable = common.which('bzr')
 
     def bzr_branch(self, **kwargs):
@@ -32,7 +32,7 @@ def bzr_branch(self, **kwargs):
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
             raise BazaarError(
-                'bzr branch for %r failed.\n%s' % (name, stderr))
+                f'bzr branch for {name!r} failed.\n{stderr}')
         if kwargs.get('verbose', False):
             return stdout
 
@@ -49,7 +49,7 @@ def bzr_pull(self, **kwargs):
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
             raise BazaarError(
-                'bzr pull for %r failed.\n%s' % (name, stderr))
+                f'bzr pull for {name!r} failed.\n{stderr}')
         if kwargs.get('verbose', False):
             return stdout
 
@@ -81,7 +81,7 @@ def matches(self):
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
             raise BazaarError(
-                'bzr info for %r failed.\n%s' % (name, stderr))
+                f'bzr info for {name!r} failed.\n{stderr}')
         return (self.source['url'] in stdout.split())
 
     def status(self, **kwargs):
diff --git a/src/mr/developer/commands.py b/src/mr/developer/commands.py
index ec70db3..4b49448 100644
--- a/src/mr/developer/commands.py
+++ b/src/mr/developer/commands.py
@@ -1,11 +1,9 @@
-from __future__ import print_function
 from mr.developer.common import logger, memoize, WorkingCopies, yesno
 import argparse
 import errno
 import os
 import re
 import shutil
-import six
 import stat
 import subprocess
 import sys
@@ -15,7 +13,7 @@
 class ChoicesPseudoAction(argparse.Action):
 
     def __init__(self, *args, **kwargs):
-        sup = super(ChoicesPseudoAction, self)
+        sup = super()
         sup.__init__(dest=args[0], option_strings=list(args), help=kwargs.get('help'), nargs=0)
 
 
@@ -36,11 +34,11 @@ def _fill_text(self, text, width, indent):
         result = []
         for line in text.split("\n"):
             for line2 in textwrap.fill(line, width).split("\n"):
-                result.append("%s%s" % (indent, line2))
+                result.append(f"{indent}{line2}")
         return "\n".join(result)
 
 
-class Command(object):
+class Command:
     def __init__(self, develop):
         self.develop = develop
 
@@ -71,7 +69,7 @@ def get_packages(self, args, auto_checkout=False,
 
         if len(result) == 0:
             if len(args) > 1:
-                regexps = "%s or '%s'" % (", ".join("'%s'" % x for x in args[:-1]), args[-1])
+                regexps = "{} or '{}'".format(", ".join("'%s'" % x for x in args[:-1]), args[-1])
             else:
                 regexps = "'%s'" % args[0]
             logger.error("No package matched %s." % regexps)
@@ -302,7 +300,7 @@ def __call__(self, args):
             for name in sorted(cmds):
                 cmd = cmds[name]
                 if len(cmd['aliases']):
-                    header = "%s (%s)" % (name, ", ".join(cmd['aliases']))
+                    header = "{} ({})".format(name, ", ".join(cmd['aliases']))
                 else:
                     header = name
                 print(header)
@@ -319,7 +317,7 @@ def __call__(self, args):
             for name in sorted(cmds):
                 cmd = cmds[name]
                 if len(cmd['aliases']):
-                    print("    %s (%s)" % (name, ", ".join(cmd['aliases'])))
+                    print("    {} ({})".format(name, ", ".join(cmd['aliases'])))
                 else:
                     print("    %s" % name)
 
@@ -464,7 +462,7 @@ def __call__(self, args):
                     else:
                         info.append("#")
             if args.long:
-                info.append("(%s) %s %s" % (source['kind'], name, source['url']))
+                info.append("({}) {} {}".format(source['kind'], name, source['url']))
             else:
                 info.append(name)
             print(" ".join(info))
@@ -560,7 +558,7 @@ def __call__(self, args):
             need_force = False
             if source['kind'] != 'svn':
                 need_force = True
-                logger.warn("The directory of package '%s' at '%s' might contain unrecoverable files and will not be removed without --force." % (name, path))
+                logger.warn(f"The directory of package '{name}' at '{path}' might contain unrecoverable files and will not be removed without --force.")
             if workingcopies.status(source) != 'clean':
                 need_force = True
                 logger.warn("The package '%s' is dirty and will not be removed without --force." % name)
@@ -578,7 +576,7 @@ def __call__(self, args):
                     if answer == 'all':
                         force_all = True
 
-            logger.info("Removing package '%s' at '%s'." % (name, path))
+            logger.info(f"Removing package '{name}' at '{path}'.")
             if not args.dry_run:
                 shutil.rmtree(source['path'],
                               ignore_errors=False,
@@ -756,7 +754,7 @@ def __call__(self, args):
             info.append(name)
             print(" ".join(info))
             if args.verbose:
-                if six.PY3 and isinstance(output, six.binary_type):
+                if isinstance(output, bytes):
                     output = output.decode('utf8')
                 output = output.strip()
                 if output:
diff --git a/src/mr/developer/common.py b/src/mr/developer/common.py
index 08d7d49..4e71ef1 100644
--- a/src/mr/developer/common.py
+++ b/src/mr/developer/common.py
@@ -2,19 +2,11 @@
 import os
 import pkg_resources
 import platform
-try:
-    import queue
-except ImportError:
-    import Queue as queue
+import queue
 import re
-import subprocess
-import six
 import sys
 import threading
-if sys.version_info < (3, ):
-    from ConfigParser import RawConfigParser
-else:
-    from configparser import RawConfigParser
+from configparser import RawConfigParser
 
 
 logger = logging.getLogger("mr.developer")
@@ -26,18 +18,6 @@ def print_stderr(s):
     sys.stderr.flush()
 
 
-try:
-    advance_iterator = next
-except NameError:
-    def advance_iterator(it):
-        return it.next()
-
-try:
-    raw_input = raw_input
-except NameError:
-    raw_input = input
-
-
 # shameless copy from
 # http://stackoverflow.com/questions/377017/test-if-executable-exists-in-python
 def which(name_root, default=None):
@@ -105,7 +85,7 @@ class WCError(Exception):
     """ A working copy error. """
 
 
-class BaseWorkingCopy(object):
+class BaseWorkingCopy:
     def __init__(self, source):
         self._output = []
         self.output = self._output.append
@@ -145,7 +125,7 @@ def yesno(question, default=True, all=True):
     else:
         question = "%s] " % question
     while 1:
-        answer = raw_input(question).lower()
+        answer = input(question).lower()
         for option in answers:
             if answer in answers[option]:
                 return option
@@ -193,7 +173,7 @@ def worker(working_copies, the_queue):
                 lvl(msg)
 
             if kwargs.get('verbose', False) and output is not None and output.strip():
-                if six.PY3 and isinstance(output, six.binary_type):
+                if isinstance(output, bytes):
                     output = output.decode('utf8')
                 print(output)
             output_lock.release()
@@ -244,7 +224,7 @@ def get_commands():
     return commands.values()
 
 
-class WorkingCopies(object):
+class WorkingCopies:
     def __init__(self, sources, threads=5):
         self.sources = sources
         self.threads = threads
@@ -255,15 +235,6 @@ def process(self, the_queue):
         if self.threads < 2:
             worker(self, the_queue)
         else:
-            if sys.version_info < (2, 6):
-                # work around a race condition in subprocess
-                _old_subprocess_cleanup = subprocess._cleanup
-
-                def _cleanup():
-                    pass
-
-                subprocess._cleanup = _cleanup
-
             threads = []
 
             for i in range(self.threads):
@@ -272,9 +243,6 @@ def _cleanup():
                 threads.append(thread)
             for thread in threads:
                 thread.join()
-            if sys.version_info < (2, 6):
-                subprocess._cleanup = _old_subprocess_cleanup
-                subprocess._cleanup()
 
         if self.errors:
             logger.error("There have been errors, see messages above.")
@@ -479,7 +447,7 @@ def parse_buildout_args(args):
     return options, settings, args
 
 
-class Rewrite(object):
+class Rewrite:
     _matcher = re.compile(r"(?P<option>^\w+) (?P<operator>[~=]{1,2}) (?P<value>.+)$")
 
     def _iter_prog_lines(self, prog):
@@ -496,14 +464,14 @@ def __init__(self, prog):
             matchdict = match.groupdict()
             option = matchdict['option']
             if option in ('name', 'path'):
-                raise ValueError("Option '%s' not allowed in rewrite:\n%s" % (option, prog))
+                raise ValueError(f"Option '{option}' not allowed in rewrite:\n{prog}")
             operator = matchdict['operator']
             rewrites = self.rewrites.setdefault(option, [])
             if operator == '~':
                 try:
-                    substitute = advance_iterator(lines)
+                    substitute = next(lines)
                 except StopIteration:
-                    raise ValueError("Missing substitution for option '%s' in rewrite:\n%s" % (option, prog))
+                    raise ValueError(f"Missing substitution for option '{option}' in rewrite:\n{prog}")
                 rewrites.append(
                     (operator, re.compile(matchdict['value']), substitute))
             elif operator == '=':
@@ -533,15 +501,15 @@ def __call__(self, source):
                     orig = source.get(option, '')
                     source[option] = operation[1].sub(operation[2], orig)
                     if source[option] != orig:
-                        logger.debug("Rewrote option '%s' from '%s' to '%s'." % (option, orig, source[option]))
+                        logger.debug(f"Rewrote option '{option}' from '{orig}' to '{source[option]}'.")
 
 
 class LegacyRewrite(Rewrite):
     def __init__(self, prefix, substitution):
-        Rewrite.__init__(self, "url ~ ^%s\n%s" % (prefix, substitution))
+        Rewrite.__init__(self, f"url ~ ^{prefix}\n{substitution}")
 
 
-class Config(object):
+class Config:
     def read_config(self, path):
         config = RawConfigParser()
         config.optionxform = lambda s: s
diff --git a/src/mr/developer/compat.py b/src/mr/developer/compat.py
deleted file mode 100644
index 0b35dde..0000000
--- a/src/mr/developer/compat.py
+++ /dev/null
@@ -1,16 +0,0 @@
-import sys
-
-
-if sys.version_info < (3, 0):
-    def b(x):
-        return x
-
-    def s(x):
-        return x
-
-else:
-    def b(x):
-        return bytes(x, "utf-8")
-
-    def s(x):
-        return str(x, "utf-8")
diff --git a/src/mr/developer/cvs.py b/src/mr/developer/cvs.py
index fd96f35..facb91a 100644
--- a/src/mr/developer/cvs.py
+++ b/src/mr/developer/cvs.py
@@ -61,7 +61,7 @@ def build_cvs_command(command, name, url, tag='', cvs_root='', tag_file=None):
 class CVSWorkingCopy(common.BaseWorkingCopy):
 
     def __init__(self, source):
-        super(CVSWorkingCopy, self).__init__(source)
+        super().__init__(source)
         if self.source.get('newest_tag', '').lower() in ['1', 'true', 'yes']:
             self.source['tag'] = self._get_newest_tag()
 
@@ -73,7 +73,7 @@ def cvs_command(self, command, **kwargs):
 
         cvs_root = self.source.get('cvs_root')
         tag_file = self.source.get('tag_file')
-        self.output((logger.info, 'Running %s %r from CVS.' % (command, name)))
+        self.output((logger.info, f'Running {command} {name!r} from CVS.'))
         cmd = build_cvs_command(command, name, url, tag, cvs_root, tag_file)
 
         # because CVS can not work on absolute paths, we must execute cvs commands
@@ -90,7 +90,7 @@ def cvs_command(self, command, **kwargs):
             os.chdir(old_cwd)
 
         if cmd.returncode != 0:
-            raise CVSError('CVS %s for %r failed.\n%s' % (command, name, stderr))
+            raise CVSError(f'CVS {command} for {name!r} failed.\n{stderr}')
         if command == 'tags':
             return self._format_tags_list(stdout)
         if kwargs.get('verbose', False):
@@ -198,5 +198,5 @@ def _get_newest_tag(self):
         if not tags:
             return None
         newest_tag = tags[0]
-        self.output((logger.info, 'Picked newest tag for %r from CVS: %r.' % (self.source['name'], newest_tag)))
+        self.output((logger.info, 'Picked newest tag for {!r} from CVS: {!r}.'.format(self.source['name'], newest_tag)))
         return newest_tag
diff --git a/src/mr/developer/darcs.py b/src/mr/developer/darcs.py
index 8ee7407..c1e6aa6 100755
--- a/src/mr/developer/darcs.py
+++ b/src/mr/developer/darcs.py
@@ -13,7 +13,7 @@ class DarcsError(common.WCError):
 class DarcsWorkingCopy(common.BaseWorkingCopy):
 
     def __init__(self, source):
-        super(DarcsWorkingCopy, self).__init__(source)
+        super().__init__(source)
         self.darcs_executable = common.which('darcs')
 
     def darcs_checkout(self, **kwargs):
@@ -28,7 +28,7 @@ def darcs_checkout(self, **kwargs):
         cmd = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise DarcsError("darcs get for '%s' failed.\n%s" % (name, stderr))
+            raise DarcsError(f"darcs get for '{name}' failed.\n{stderr}")
         if kwargs.get('verbose', False):
             return stdout
 
@@ -42,7 +42,7 @@ def darcs_update(self, **kwargs):
                                stderr=subprocess.PIPE)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise DarcsError("darcs pull for '%s' failed.\n%s" % (name, stderr))
+            raise DarcsError(f"darcs pull for '{name}' failed.\n{stderr}")
         if kwargs.get('verbose', False):
             return stdout
 
@@ -56,7 +56,7 @@ def checkout(self, **kwargs):
             elif self.matches():
                 self.output((logger.info, "Skipped checkout of existing package '%s'." % name))
             else:
-                raise DarcsError("Checkout URL for existing package '%s' differs. Expected '%s'." % (name, self.source['url']))
+                raise DarcsError("Checkout URL for existing package '{}' differs. Expected '{}'.".format(name, self.source['url']))
         else:
             return self.darcs_checkout(**kwargs)
 
@@ -74,7 +74,7 @@ def _darcs_related_repositories(self):
                                    stderr=subprocess.PIPE)
             stdout, stderr = cmd.communicate()
             if cmd.returncode != 0:
-                self.output((logger.error, "darcs info for '%s' failed.\n%s" % (name, stderr)))
+                self.output((logger.error, f"darcs info for '{name}' failed.\n{stderr}"))
                 return
 
             lines = stdout.splitlines()
diff --git a/src/mr/developer/develop.py b/src/mr/developer/develop.py
index d892510..b595bc3 100644
--- a/src/mr/developer/develop.py
+++ b/src/mr/developer/develop.py
@@ -22,7 +22,7 @@ def find_base():
             path = None
             break
     if path is None:
-        raise IOError(".mr.developer.cfg not found")
+        raise OSError(".mr.developer.cfg not found")
 
     return path
 
@@ -44,11 +44,11 @@ def _fill_text(self, text, width, indent):
         result = []
         for line in text.split("\n"):
             for line2 in textwrap.fill(line, width).split("\n"):
-                result.append("%s%s" % (indent, line2))
+                result.append(f"{indent}{line2}")
         return "\n".join(result)
 
 
-class Develop(object):
+class Develop:
     def __call__(self, *args, **kwargs):
         logger.setLevel(logging.INFO)
         ch = logging.StreamHandler()
@@ -70,7 +70,7 @@ def __call__(self, *args, **kwargs):
 
         try:
             self.buildout_dir = find_base()
-        except IOError:
+        except OSError:
             if isinstance(args.func, CmdHelp):
                 args.func(args)
                 return
diff --git a/src/mr/developer/extension.py b/src/mr/developer/extension.py
index 21051ec..d8c5107 100644
--- a/src/mr/developer/extension.py
+++ b/src/mr/developer/extension.py
@@ -26,7 +26,7 @@ def exists(self):
         return os.path.exists(self['path'])
 
 
-class Extension(object):
+class Extension:
     def __init__(self, buildout):
         self.buildout = buildout
         self.buildout_dir = buildout['buildout']['directory']
@@ -90,7 +90,7 @@ def get_sources(self):
                 sys.exit(1)
             kind = info[0]
             if kind not in workingcopytypes:
-                logger.error("Unknown repository type '%s' for source '%s'." % (kind, name))
+                logger.error(f"Unknown repository type '{kind}' for source '{name}'.")
                 sys.exit(1)
             url = info[1]
 
@@ -119,7 +119,7 @@ def get_sources(self):
                     # ``foo += branch=my-feature`` refining the ``branch`` set
                     # in a shared/extended source definition.
                     logger.info(
-                        "Overriding '%s' for source '%s'." % (key, name))
+                        f"Overriding '{key}' for source '{name}'.")
                 if key == 'path':
                     value = os.path.join(value, name)
                     if not os.path.isabs(value):
@@ -168,7 +168,7 @@ def get_auto_checkout(self):
         if not auto_checkout.issubset(packages):
             diff = list(sorted(auto_checkout.difference(packages)))
             if len(diff) > 1:
-                pkgs = "%s and '%s'" % (", ".join("'%s'" % x for x in diff[:-1]), diff[-1])
+                pkgs = "{} and '{}'".format(", ".join("'%s'" % x for x in diff[:-1]), diff[-1])
                 logger.error("The packages %s from auto-checkout have no source information." % pkgs)
             else:
                 logger.error("The package '%s' from auto-checkout has no source information." % diff[0])
diff --git a/src/mr/developer/git.py b/src/mr/developer/git.py
index df1c180..965eab9 100644
--- a/src/mr/developer/git.py
+++ b/src/mr/developer/git.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 from mr.developer import common
 import os
 import subprocess
@@ -42,7 +40,7 @@ def __init__(self, source):
                          "(%s) in source for %s",
                          source['branch'], source['rev'], source['name'])
             sys.exit(1)
-        super(GitWorkingCopy, self).__init__(source)
+        super().__init__(source)
 
     @common.memoize
     def git_version(self):
@@ -50,13 +48,13 @@ def git_version(self):
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
             logger.error("Could not determine git version")
-            logger.error("'git --version' output was:\n%s\n%s" % (stdout, stderr))
+            logger.error(f"'git --version' output was:\n{stdout}\n{stderr}")
             sys.exit(1)
 
         m = re.search(r"git version (\d+)\.(\d+)(\.\d+)?(\.\d+)?", stdout)
         if m is None:
             logger.error("Unable to parse git version output")
-            logger.error("'git --version' output was:\n%s\n%s" % (stdout, stderr))
+            logger.error(f"'git --version' output was:\n{stdout}\n{stderr}")
             sys.exit(1)
         version = m.groups()
 
@@ -122,10 +120,10 @@ def git_merge_rbranch(self, stdout_in, stderr_in, accept_missing=False):
                 sys.exit(1)
 
         rbp = self._remote_branch_prefix
-        cmd = self.run_git(["merge", "%s/%s" % (rbp, branch)], cwd=path)
+        cmd = self.run_git(["merge", f"{rbp}/{branch}"], cwd=path)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise GitError("git merge of remote branch 'origin/%s' failed.\n%s" % (branch, stderr))
+            raise GitError(f"git merge of remote branch 'origin/{branch}' failed.\n{stderr}")
         return (stdout_in + stdout,
                 stderr_in + stderr)
 
@@ -150,7 +148,7 @@ def git_checkout(self, **kwargs):
         cmd = self.run_git(args)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise GitError("git cloning of '%s' failed.\n%s" % (name, stderr))
+            raise GitError(f"git cloning of '{name}' failed.\n{stderr}")
         if 'rev' in self.source:
             stdout, stderr = self.git_switch_branch(stdout, stderr)
         if 'pushurl' in self.source:
@@ -163,7 +161,7 @@ def git_checkout(self, **kwargs):
             # as git submodule update on modified submodules may cause code loss
             for submodule in initialized:
                 stdout, stderr = self.git_update_submodules(stdout, stderr, submodule=submodule)
-                self.output((logger.info, "Initialized '%s' submodule at '%s' with git." % (name, submodule)))
+                self.output((logger.info, f"Initialized '{name}' submodule at '{submodule}' with git."))
 
         if kwargs.get('verbose', False):
             return stdout
@@ -195,7 +193,7 @@ def git_switch_branch(self, stdout_in, stderr_in, accept_missing=False):
                 "^  " + re.escape(rbp) + r"\/" + re.escape(branch) + "$",
                 stdout, re.M):
             # the branch is not local, normal checkout won't work here
-            rbranch = "%s/%s" % (rbp, branch)
+            rbranch = f"{rbp}/{branch}"
             argv = ["checkout", "-b", branch, rbranch]
             self.output((logger.info, "Switching to remote branch '%s'." % rbranch))
         elif accept_missing:
@@ -209,7 +207,7 @@ def git_switch_branch(self, stdout_in, stderr_in, accept_missing=False):
         cmd = self.run_git(argv, cwd=path)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise GitError("git checkout of branch '%s' failed.\n%s" % (branch, stderr))
+            raise GitError(f"git checkout of branch '{branch}' failed.\n{stderr}")
         return (stdout_in + stdout,
                 stderr_in + stderr)
 
@@ -222,7 +220,7 @@ def git_update(self, **kwargs):
         cmd = self.run_git(argv, cwd=path)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise GitError("git fetch of '%s' failed.\n%s" % (name, stderr))
+            raise GitError(f"git fetch of '{name}' failed.\n{stderr}")
         if 'rev' in self.source:
             stdout, stderr = self.git_switch_branch(stdout, stderr)
         elif 'branch' in self.source:
@@ -241,7 +239,7 @@ def git_update(self, **kwargs):
             # as git submodule update on modified subomdules may cause code loss
             for submodule in initialized:
                 stdout, stderr = self.git_update_submodules(stdout, stderr, submodule=submodule)
-                self.output((logger.info, "Initialized '%s' submodule at '%s' with git." % (name, submodule)))
+                self.output((logger.info, f"Initialized '{name}' submodule at '{submodule}' with git."))
 
         if kwargs.get('verbose', False):
             return stdout
@@ -256,7 +254,7 @@ def checkout(self, **kwargs):
             elif self.matches():
                 self.output((logger.info, "Skipped checkout of existing package '%s'." % name))
             else:
-                self.output((logger.warning, "Checkout URL for existing package '%s' differs. Expected '%s'." % (name, self.source['url'])))
+                self.output((logger.warning, "Checkout URL for existing package '{}' differs. Expected '{}'.".format(name, self.source['url'])))
         else:
             return self.git_checkout(**kwargs)
 
@@ -286,7 +284,7 @@ def matches(self):
                            cwd=path)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise GitError("git remote of '%s' failed.\n%s" % (name, stderr))
+            raise GitError(f"git remote of '{name}' failed.\n{stderr}")
         return (self.source['url'] in stdout.split())
 
     def update(self, **kwargs):
@@ -307,7 +305,7 @@ def git_set_pushurl(self, stdout_in, stderr_in):
         stdout, stderr = cmd.communicate()
 
         if cmd.returncode != 0:
-            raise GitError("git config remote.%s.pushurl %s \nfailed.\n" % (self._upstream_name, self.source['pushurl']))
+            raise GitError("git config remote.{}.pushurl {} \nfailed.\n".format(self._upstream_name, self.source['pushurl']))
         return (stdout_in + stdout, stderr_in + stderr)
 
     def git_init_submodules(self, stdout_in, stderr_in):
diff --git a/src/mr/developer/gitsvn.py b/src/mr/developer/gitsvn.py
index 6957b27..7d53279 100644
--- a/src/mr/developer/gitsvn.py
+++ b/src/mr/developer/gitsvn.py
@@ -13,7 +13,7 @@ class GitSVNError(common.WCError):
 class GitSVNWorkingCopy(SVNWorkingCopy):
 
     def __init__(self, source):
-        super(GitSVNWorkingCopy, self).__init__(source)
+        super().__init__(source)
         self.gitify_executable = common.which('gitify')
 
     def gitify_init(self, **kwargs):
@@ -27,16 +27,16 @@ def gitify_init(self, **kwargs):
             stderr=subprocess.PIPE)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise GitSVNError("gitify init for '%s' failed.\n%s" % (name, stdout))
+            raise GitSVNError(f"gitify init for '{name}' failed.\n{stdout}")
         if kwargs.get('verbose', False):
             return stdout
 
     def svn_checkout(self, **kwargs):
-        super(GitSVNWorkingCopy, self).svn_checkout(**kwargs)
+        super().svn_checkout(**kwargs)
         return self.gitify_init(**kwargs)
 
     def svn_switch(self, **kwargs):
-        super(GitSVNWorkingCopy, self).svn_switch(**kwargs)
+        super().svn_switch(**kwargs)
         return self.gitify_init(**kwargs)
 
     def svn_update(self, **kwargs):
@@ -50,12 +50,12 @@ def svn_update(self, **kwargs):
             stderr=subprocess.PIPE)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise GitSVNError("gitify update for '%s' failed.\n%s" % (name, stdout))
+            raise GitSVNError(f"gitify update for '{name}' failed.\n{stdout}")
         if kwargs.get('verbose', False):
             return stdout
 
     def status(self, **kwargs):
-        svn_status = super(GitSVNWorkingCopy, self).status(**kwargs)
+        svn_status = super().status(**kwargs)
         if svn_status == 'clean':
             return common.get_workingcopytypes()['git'](
                 self.source).status(**kwargs)
diff --git a/src/mr/developer/mercurial.py b/src/mr/developer/mercurial.py
index e4ab5d9..775bc24 100644
--- a/src/mr/developer/mercurial.py
+++ b/src/mr/developer/mercurial.py
@@ -1,5 +1,4 @@
 from mr.developer import common
-from mr.developer.compat import b
 import re
 import os
 import subprocess
@@ -17,7 +16,7 @@ def __init__(self, source):
         self.hg_executable = common.which('hg')
         source.setdefault('branch', 'default')
         source.setdefault('rev')
-        super(MercurialWorkingCopy, self).__init__(source)
+        super().__init__(source)
 
     def hg_clone(self, **kwargs):
         name = self.source['name']
@@ -37,7 +36,7 @@ def hg_clone(self, **kwargs):
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
             raise MercurialError(
-                'hg clone for %r failed.\n%s' % (name, stderr))
+                f'hg clone for {name!r} failed.\n{stderr}')
         if kwargs.get('verbose', False):
             return stdout
 
@@ -68,8 +67,8 @@ def _update_to_rev(self, rev):
         stdout, stderr = cmd.communicate()
         if cmd.returncode:
             raise MercurialError(
-                'hg update for %r failed.\n%s' % (name, stderr))
-        self.output((logger.info, 'Switched %r to %s.' % (name, rev)))
+                f'hg update for {name!r} failed.\n{stderr}')
+        self.output((logger.info, f'Switched {name!r} to {rev}.'))
         return stdout
 
     def _get_tags(self):
@@ -86,7 +85,7 @@ def _get_tags(self):
         stdout, stderr = cmd.communicate()
         if cmd.returncode:
             raise MercurialError(
-                'hg update for %r failed.\n%s' % (name, stderr))
+                f'hg update for {name!r} failed.\n{stderr}')
 
         tag_line_re = re.compile(r'([^\s]+)[\s]*.*')
 
@@ -108,7 +107,7 @@ def _get_newest_tag(self):
         if not tags:
             return None
         newest_tag = tags[0]
-        self.output((logger.info, 'Picked newest tag for %r from Mercurial: %r.' % (name, newest_tag)))
+        self.output((logger.info, f'Picked newest tag for {name!r} from Mercurial: {newest_tag!r}.'))
         return newest_tag
 
     def hg_pull(self, **kwargs):
@@ -129,7 +128,7 @@ def hg_pull(self, **kwargs):
             # no remote changes.
             if 'no changes found' not in stdout:
                 raise MercurialError(
-                    'hg pull for %r failed.\n%s' % (name, stderr))
+                    f'hg pull for {name!r} failed.\n{stderr}')
         # to find newest_tag hg pull is needed before
         rev = self.get_rev()
         if rev:
@@ -164,9 +163,9 @@ def matches(self):
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
             raise MercurialError(
-                'hg showconfig for %r failed.\n%s' % (name, stderr))
+                f'hg showconfig for {name!r} failed.\n{stderr}')
         # now check that the working branch is the same
-        return b(self.source['url'] + '\n') == stdout
+        return self.source['url'].encode('utf-8') + b'\n' == stdout
 
     def status(self, **kwargs):
         path = self.source['path']
@@ -182,7 +181,7 @@ def status(self, **kwargs):
                 [self.hg_executable, 'outgoing'], cwd=path,
                 env=env, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             outgoing_stdout, stderr = cmd.communicate()
-            stdout += b('\n') + outgoing_stdout
+            stdout += b'\n' + outgoing_stdout
             if cmd.returncode == 0:
                 status = 'ahead'
         if kwargs.get('verbose', False):
diff --git a/src/mr/developer/svn.py b/src/mr/developer/svn.py
index 7551f22..233d0a7 100644
--- a/src/mr/developer/svn.py
+++ b/src/mr/developer/svn.py
@@ -1,14 +1,6 @@
 from mr.developer import common
-from mr.developer.compat import b, s
-try:
-    from urllib.parse import urlparse, urlunparse
-except ImportError:
-    from urlparse import urlparse, urlunparse
-try:
-    import xml.etree.ElementTree as etree
-    etree  # shutup pyflakes
-except ImportError:
-    import elementtree.ElementTree as etree
+from urllib.parse import urlparse, urlunparse
+import xml.etree.ElementTree as etree
 import getpass
 import os
 import re
@@ -16,12 +8,6 @@
 import sys
 
 
-try:
-    raw_input = raw_input
-except NameError:
-    raw_input = input
-
-
 logger = common.logger
 
 
@@ -87,10 +73,10 @@ def _svn_check_version(self):
                 sys.exit(1)
             raise
         stdout, stderr = cmd.communicate()
-        lines = stdout.split(b('\n'))
+        lines = stdout.split(b'\n')
         version = None
         if len(lines):
-            version = re.search(b(r'(\d+)\.(\d+)(\.\d+)?'), lines[0])
+            version = re.search(br'(\d+)\.(\d+)(\.\d+)?', lines[0])
             if version is not None:
                 version = version.groups()
                 if len(version) == 3:
@@ -99,7 +85,7 @@ def _svn_check_version(self):
                     version = (int(version[0]), int(version[1]))
         if (cmd.returncode != 0) or (version is None):
             logger.error("Couldn't determine the version of 'svn' command.")
-            logger.error("Subversion output:\n%s\n%s" % (s(stdout), s(stderr)))
+            logger.error(f"Subversion output:\n{stdout.decode('utf-8')}\n{stderr.decode('utf-8')}")
             sys.exit(1)
         if (version < (1, 5)) and not _svn_version_warning:
             logger.warning("The installed 'svn' command is too old. Expected 1.5 or newer, got %s." % ".".join([str(x) for x in version]))
@@ -133,8 +119,8 @@ def _svn_error_wrapper(self, f, **kwargs):
                     common.input_lock.release()
                     common.output_lock.release()
                     continue
-                print("Authorization needed for '%s' at '%s'" % (self.source['name'], self.source['url']))
-                user = raw_input("Username: ")
+                print("Authorization needed for '{}' at '{}'".format(self.source['name'], self.source['url']))
+                user = input("Username: ")
                 passwd = getpass.getpass("Password: ")
                 self._svn_auth_cache[root] = dict(
                     user=user,
@@ -156,7 +142,7 @@ def _svn_error_wrapper(self, f, **kwargs):
                     continue
                 print("\n".join(lines[:-1]))
                 while 1:
-                    answer = raw_input("(R)eject or accept (t)emporarily? ")
+                    answer = input("(R)eject or accept (t)emporarily? ")
                     if answer.lower() in ['r', 't']:
                         break
                     else:
@@ -176,9 +162,9 @@ def _svn_checkout(self, **kwargs):
         args = [self.svn_executable, "checkout", url, path]
         stdout, stderr, returncode = self._svn_communicate(args, url, **kwargs)
         if returncode != 0:
-            raise SVNError("Subversion checkout for '%s' failed.\n%s" % (name, s(stderr)))
+            raise SVNError(f"Subversion checkout for '{name}' failed.\n{stderr.decode('utf-8')}")
         if kwargs.get('verbose', False):
-            return s(stdout)
+            return stdout.decode("utf-8")
 
     def _svn_communicate(self, args, url, **kwargs):
         auth = self._svn_auth_get(url)
@@ -203,7 +189,7 @@ def _svn_communicate(self, args, url, **kwargs):
                                stderr=subprocess.PIPE)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            lines = stderr.strip().split(b('\n'))
+            lines = stderr.strip().split(b'\n')
             if 'authorization failed' in lines[-1] or 'Could not authenticate to server' in lines[-1]:
                 raise SVNAuthorizationError(stderr.strip())
             if 'Server certificate verification failed: issuer is not trusted' in lines[-1]:
@@ -226,7 +212,7 @@ def _svn_info(self):
                                stderr=subprocess.PIPE)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise SVNError("Subversion info for '%s' failed.\n%s" % (name, s(stderr)))
+            raise SVNError(f"Subversion info for '{name}' failed.\n{stderr.decode('utf-8')}")
         info = etree.fromstring(stdout)
         result = {}
         entry = info.find('entry')
@@ -254,9 +240,9 @@ def _svn_switch(self, **kwargs):
             args.insert(2, '-r%s' % rev)
         stdout, stderr, returncode = self._svn_communicate(args, url, **kwargs)
         if returncode != 0:
-            raise SVNError("Subversion switch of '%s' failed.\n%s" % (name, s(stderr)))
+            raise SVNError(f"Subversion switch of '{name}' failed.\n{stderr.decode('utf-8')}")
         if kwargs.get('verbose', False):
-            return s(stdout)
+            return stdout.decode("utf-8")
 
     def _svn_update(self, **kwargs):
         name = self.source['name']
@@ -267,9 +253,9 @@ def _svn_update(self, **kwargs):
             args.insert(2, '-r%s' % rev)
         stdout, stderr, returncode = self._svn_communicate(args, url, **kwargs)
         if returncode != 0:
-            raise SVNError("Subversion update of '%s' failed.\n%s" % (name, s(stderr)))
+            raise SVNError(f"Subversion update of '{name}' failed.\n{stderr.decode('utf-8')}")
         if kwargs.get('verbose', False):
-            return s(stdout)
+            return stdout.decode("utf-8")
 
     def svn_checkout(self, **kwargs):
         name = self.source['name']
@@ -307,10 +293,10 @@ def checkout(self, **kwargs):
                 else:
                     url = self._svn_info().get('url', '')
                     if url:
-                        msg = "The current checkout of '%s' is from '%s'." % (name, url)
+                        msg = f"The current checkout of '{name}' is from '{url}'."
                         msg += "\nCan't switch package to '%s' because it's dirty." % (self.source['url'])
                     else:
-                        msg = "Can't switch package '%s' to '%s' because it's dirty." % (name, self.source['url'])
+                        msg = "Can't switch package '{}' to '{}' because it's dirty.".format(name, self.source['url'])
                     raise SVNError(msg)
         else:
             return self.svn_checkout(**kwargs)
@@ -337,7 +323,7 @@ def status(self, **kwargs):
                                stderr=subprocess.PIPE)
         stdout, stderr = cmd.communicate()
         if cmd.returncode != 0:
-            raise SVNError("Subversion status for '%s' failed.\n%s" % (name, s(stderr)))
+            raise SVNError(f"Subversion status for '{name}' failed.\n{stderr.decode('utf-8')}")
         info = etree.fromstring(stdout)
         clean = True
         for target in info.findall('target'):
@@ -356,8 +342,8 @@ def status(self, **kwargs):
                                    stderr=subprocess.PIPE)
             stdout, stderr = cmd.communicate()
             if cmd.returncode != 0:
-                raise SVNError("Subversion status for '%s' failed.\n%s" % (name, s(stderr)))
-            return status, s(stdout)
+                raise SVNError(f"Subversion status for '{name}' failed.\n{stderr.decode('utf-8')}")
+            return status, stdout.decode("utf-8")
         else:
             return status
 
diff --git a/src/mr/developer/tests/test_commands.py b/src/mr/developer/tests/test_commands.py
index 2263c6d..9f7df50 100644
--- a/src/mr/developer/tests/test_commands.py
+++ b/src/mr/developer/tests/test_commands.py
@@ -1,4 +1,4 @@
-from mock import patch
+from unittest.mock import patch
 import pytest
 
 
@@ -12,40 +12,40 @@ class TestCommand:
     def command(self, develop):
         from mr.developer.commands import Command
         develop.sources = ['foo', 'bar', 'baz', 'ham']
-        develop.auto_checkout = set(['foo', 'ham'])
+        develop.auto_checkout = {'foo', 'ham'}
         return Command(develop)
 
     def testEmptyMatchList(self, command):
         pkgs = command.get_packages([])
-        assert pkgs == set(['foo', 'bar', 'baz', 'ham'])
+        assert pkgs == {'foo', 'bar', 'baz', 'ham'}
 
     def testEmptyMatchListAuto(self, command):
         pkgs = command.get_packages([], auto_checkout=True)
-        assert pkgs == set(['foo', 'ham'])
+        assert pkgs == {'foo', 'ham'}
 
     def testSingleArgMatchingOne(self, command):
         pkgs = command.get_packages(['ha'])
-        assert pkgs == set(['ham'])
+        assert pkgs == {'ham'}
 
     def testSingleArgMatchingMultiple(self, command):
         pkgs = command.get_packages(['ba'])
-        assert pkgs == set(['bar', 'baz'])
+        assert pkgs == {'bar', 'baz'}
 
     def testArgsMatchingOne(self, command):
         pkgs = command.get_packages(['ha', 'zap'])
-        assert pkgs == set(['ham'])
+        assert pkgs == {'ham'}
 
     def testArgsMatchingMultiple(self, command):
         pkgs = command.get_packages(['ba', 'zap'])
-        assert pkgs == set(['bar', 'baz'])
+        assert pkgs == {'bar', 'baz'}
 
     def testArgsMatchingMultiple2(self, command):
         pkgs = command.get_packages(['ha', 'ba'])
-        assert pkgs == set(['bar', 'baz', 'ham'])
+        assert pkgs == {'bar', 'baz', 'ham'}
 
     def testSingleArgMatchingOneAuto(self, command):
         pkgs = command.get_packages(['ha'], auto_checkout=True)
-        assert pkgs == set(['ham'])
+        assert pkgs == {'ham'}
 
     def testSingleArgMatchingMultipleAuto(self, command):
         pytest.raises(
@@ -54,7 +54,7 @@ def testSingleArgMatchingMultipleAuto(self, command):
 
     def testArgsMatchingOneAuto(self, command):
         pkgs = command.get_packages(['ha', 'zap'], auto_checkout=True)
-        assert pkgs == set(['ham'])
+        assert pkgs == {'ham'}
 
     def testArgsMatchingMultipleAuto(self, command):
         pytest.raises(
@@ -63,7 +63,7 @@ def testArgsMatchingMultipleAuto(self, command):
 
     def testArgsMatchingMultiple2Auto(self, command):
         pkgs = command.get_packages(['ha', 'ba'], auto_checkout=True)
-        assert pkgs == set(['ham'])
+        assert pkgs == {'ham'}
 
 
 class TestDeactivateCommand:
@@ -74,7 +74,7 @@ def develop(self, develop):
             bar=MockSource(),
             baz=MockSource(),
             ham=MockSource())
-        develop.auto_checkout = set(['foo', 'ham'])
+        develop.auto_checkout = {'foo', 'ham'}
         develop.config.develop['foo'] = 'auto'
         develop.config.develop['ham'] = 'auto'
         return develop
diff --git a/src/mr/developer/tests/test_extension.py b/src/mr/developer/tests/test_extension.py
index bbd0870..520ea66 100644
--- a/src/mr/developer/tests/test_extension.py
+++ b/src/mr/developer/tests/test_extension.py
@@ -1,5 +1,5 @@
 from copy import deepcopy
-from mock import patch
+from unittest.mock import patch
 from mr.developer.extension import Extension
 from mr.developer.tests.utils import MockConfig
 from zc.buildout.buildout import MissingSection
@@ -7,7 +7,7 @@
 import pytest
 
 
-class MockBuildout(object):
+class MockBuildout:
     def __init__(self, config=None):
         if config is None:
             config = dict()
@@ -32,7 +32,7 @@ def __repr__(self):
         return repr(self._raw)
 
 
-class MockWorkingCopies(object):
+class MockWorkingCopies:
     def __init__(self, sources):
         self.sources = sources
         self._events = []
diff --git a/src/mr/developer/tests/test_git.py b/src/mr/developer/tests/test_git.py
index 9611874..415a132 100644
--- a/src/mr/developer/tests/test_git.py
+++ b/src/mr/developer/tests/test_git.py
@@ -2,7 +2,7 @@
 import shutil
 
 import pytest
-from mock import patch
+from unittest.mock import patch
 
 from mr.developer.extension import Source
 from mr.developer.tests.utils import Process
@@ -41,9 +41,9 @@ def testUpdateWithRevisionPin(self, develop, mkgitrepo, src):
                 url='%s' % repository.base,
                 path=src['egg'])}
         CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-        assert set(os.listdir(src['egg'])) == set(('.git', 'foo', 'foo2'))
+        assert set(os.listdir(src['egg'])) == {'.git', 'foo', 'foo2'}
         CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-        assert set(os.listdir(src['egg'])) == set(('.git', 'foo', 'foo2'))
+        assert set(os.listdir(src['egg'])) == {'.git', 'foo', 'foo2'}
 
         shutil.rmtree(src['egg'])
 
@@ -63,9 +63,9 @@ def testUpdateWithBranch(self, develop, mkgitrepo, src):
                 url='%s' % repository.base,
                 path=src['egg'])}
         CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-        assert set(os.listdir(src['egg'])) == set(('.git', 'foo', 'foo2'))
+        assert set(os.listdir(src['egg'])) == {'.git', 'foo', 'foo2'}
         CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-        assert set(os.listdir(src['egg'])) == set(('.git', 'foo', 'foo2'))
+        assert set(os.listdir(src['egg'])) == {'.git', 'foo', 'foo2'}
         CmdStatus(develop)(develop.parser.parse_args(['status']))
 
     def testUpdateWithMain(self, develop, mkgitrepo, src):
@@ -80,9 +80,9 @@ def testUpdateWithMain(self, develop, mkgitrepo, src):
                 url='%s' % repository.base,
                 path=src['egg'])}
         CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-        assert set(os.listdir(src['egg'])) == set(('.git', 'bar', 'foo'))
+        assert set(os.listdir(src['egg'])) == {'.git', 'bar', 'foo'}
         CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-        assert set(os.listdir(src['egg'])) == set(('.git', 'bar', 'foo'))
+        assert set(os.listdir(src['egg'])) == {'.git', 'bar', 'foo'}
 
     def testRaiseExceptionUpdateWithRevisionAndBranch(self, develop, mkgitrepo, src):
         from mr.developer.commands import CmdCheckout
@@ -118,11 +118,11 @@ def testUpdateWithoutRevisionPin(self, develop, mkgitrepo, src, capsys):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('.git', 'bar', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'.git', 'bar', 'foo'}
             captured = capsys.readouterr()
             assert captured.out.startswith("Initialized empty Git repository in")
             CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('.git', 'bar', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'.git', 'bar', 'foo'}
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with git from '%s'." % repository.url,), {}),
                 ('info', ("Updated 'egg' with git.",), {}),
@@ -154,11 +154,11 @@ def testUpdateVerbose(self, develop, mkgitrepo, src, capsys):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg', '-v']))
-            assert set(os.listdir(src['egg'])) == set(('.git', 'bar', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'.git', 'bar', 'foo'}
             captured = capsys.readouterr()
             assert captured.out.startswith("Initialized empty Git repository in")
             CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg', '-v']))
-            assert set(os.listdir(src['egg'])) == set(('.git', 'bar', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'.git', 'bar', 'foo'}
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with git from '%s'." % repository.url,), {}),
                 ('info', ("Updated 'egg' with git.",), {}),
@@ -254,4 +254,4 @@ def testDepthOption(self, mkgitrepo, src, tempdir):
         assert len(commits) == 1
 
         # Check that the expected files from the branch are there
-        assert set(os.listdir(src['egg'])) == set(('.git', 'foo', 'foo2'))
+        assert set(os.listdir(src['egg'])) == {'.git', 'foo', 'foo2'}
diff --git a/src/mr/developer/tests/test_git_submodules.py b/src/mr/developer/tests/test_git_submodules.py
index 5e116c9..45a3472 100644
--- a/src/mr/developer/tests/test_git_submodules.py
+++ b/src/mr/developer/tests/test_git_submodules.py
@@ -1,4 +1,4 @@
-from mock import patch
+from unittest.mock import patch
 from mr.developer.extension import Source
 from mr.developer.tests.utils import GitRepo
 import os
@@ -27,8 +27,8 @@ def testCheckoutWithSubmodule(self, develop, mkgitrepo, src):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_name])) == set(('.git', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_name])) == {'.git', 'foo'}
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with git from '%s'." % egg.url,), {}),
                 ('info', ("Initialized 'egg' submodule at '%s' with git." % submodule_name,), {})]
@@ -63,9 +63,9 @@ def testCheckoutWithTwoSubmodules(self, develop, mkgitrepo, src):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', 'submodule_b', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_name])) == set(('.git', 'foo'))
-            assert set(os.listdir(src['egg/%s' % submodule_b_name])) == set(('.git', 'foo_b'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', 'submodule_b', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_name])) == {'.git', 'foo'}
+            assert set(os.listdir(src['egg/%s' % submodule_b_name])) == {'.git', 'foo_b'}
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with git from '%s'." % egg.url,), {}),
                 ('info', ("Initialized 'egg' submodule at '%s' with git." % submodule_name,), {}),
@@ -96,8 +96,8 @@ def testUpdateWithSubmodule(self, develop, mkgitrepo, src):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_name])) == set(('.git', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_name])) == {'.git', 'foo'}
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with git from '%s'." % egg.url,), {}),
                 ('info', ("Initialized 'egg' submodule at '%s' with git." % submodule_name,), {})]
@@ -112,8 +112,8 @@ def testUpdateWithSubmodule(self, develop, mkgitrepo, src):
         log = _log.__enter__()
         try:
             CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', 'submodule_b', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_b_name])) == set(('.git', 'foo_b'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', 'submodule_b', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_b_name])) == {'.git', 'foo_b'}
             assert log.method_calls == [
                 ('info', ("Updated 'egg' with git.",), {}),
                 ('info', ("Switching to branch 'master'.",), {}),
@@ -146,7 +146,7 @@ def testCheckoutWithSubmodulesOptionNever(self, develop, mkgitrepo, src):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
             assert set(os.listdir(src['egg/%s' % submodule_name])) == set()
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with git from '%s'." % egg.url,), {})]
@@ -189,9 +189,9 @@ def testCheckoutWithSubmodulesOptionNeverSourceAlways(self, develop, mkgitrepo,
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_name])) == set(('foo', '.git'))
-            assert set(os.listdir(src['egg2'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_name])) == {'foo', '.git'}
+            assert set(os.listdir(src['egg2'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
             assert set(os.listdir(src['egg2/%s' % submodule_name])) == set()
 
             assert log.method_calls == [
@@ -236,9 +236,9 @@ def testCheckoutWithSubmodulesOptionAlwaysSourceNever(self, develop, mkgitrepo,
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_name])) == set(('foo', '.git'))
-            assert set(os.listdir(src['egg2'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_name])) == {'foo', '.git'}
+            assert set(os.listdir(src['egg2'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
             assert set(os.listdir(src['egg2/%s' % submodule_name])) == set()
 
             assert log.method_calls == [
@@ -272,8 +272,8 @@ def testUpdateWithSubmoduleCheckout(self, develop, mkgitrepo, src):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_name])) == set(('.git', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_name])) == {'.git', 'foo'}
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with git from '%s'." % egg.url,), {}),
                 ('info', ("Initialized 'egg' submodule at '%s' with git." % submodule_name,), {})]
@@ -288,7 +288,7 @@ def testUpdateWithSubmoduleCheckout(self, develop, mkgitrepo, src):
         log = _log.__enter__()
         try:
             CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', 'submodule_b', '.git', 'bar', '.gitmodules'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', 'submodule_b', '.git', 'bar', '.gitmodules'}
             assert set(os.listdir(src['egg/%s' % submodule_b_name])) == set()
             assert log.method_calls == [
                 ('info', ("Updated 'egg' with git.",), {}),
@@ -320,8 +320,8 @@ def testUpdateWithSubmoduleDontUpdatePreviousSubmodules(self, develop, mkgitrepo
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_name])) == set(('.git', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_name])) == {'.git', 'foo'}
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with git from '%s'." % egg.url,), {}),
                 ('info', ("Initialized 'egg' submodule at '%s' with git." % submodule_name,), {})]
@@ -335,8 +335,8 @@ def testUpdateWithSubmoduleDontUpdatePreviousSubmodules(self, develop, mkgitrepo
         log = _log.__enter__()
         try:
             CmdUpdate(develop)(develop.parser.parse_args(['up', '-f', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('submodule_a', '.git', 'bar', '.gitmodules'))
-            assert set(os.listdir(src['egg/%s' % submodule_name])) == set(('.git', 'foo', 'newfile'))
+            assert set(os.listdir(src['egg'])) == {'submodule_a', '.git', 'bar', '.gitmodules'}
+            assert set(os.listdir(src['egg/%s' % submodule_name])) == {'.git', 'foo', 'newfile'}
             assert log.method_calls == [
                 ('info', ("Updated 'egg' with git.",), {}),
                 ('info', ("Switching to branch 'master'.",), {})]
diff --git a/src/mr/developer/tests/test_mercurial.py b/src/mr/developer/tests/test_mercurial.py
index b6ba6a5..3e416cd 100644
--- a/src/mr/developer/tests/test_mercurial.py
+++ b/src/mr/developer/tests/test_mercurial.py
@@ -1,11 +1,10 @@
 import os
 
 import pytest
-from mock import patch
+from unittest.mock import patch
 
 from mr.developer.extension import Source
 from mr.developer.tests.utils import Process
-from mr.developer.compat import b
 
 
 class TestMercurial:
@@ -35,9 +34,9 @@ def testUpdateWithoutRevisionPin(self, develop, src, tempdir):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(os.path.join(src, 'egg'))) == set(('.hg', 'bar', 'foo'))
+            assert set(os.listdir(os.path.join(src, 'egg'))) == {'.hg', 'bar', 'foo'}
             CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-            assert set(os.listdir(os.path.join(src, 'egg'))) == set(('.hg', 'bar', 'foo'))
+            assert set(os.listdir(os.path.join(src, 'egg'))) == {'.hg', 'bar', 'foo'}
             assert log.method_calls == [
                 ('info', ("Cloned 'egg' with mercurial.",), {}),
                 ('info', ("Updated 'egg' with mercurial.",), {}),
@@ -66,7 +65,7 @@ def testUpdateWithRevisionPin(self, develop, src, tempdir):
 
         try:
             # XXX older version
-            rev = lines[0].split()[1].split(b(':'))[1]
+            rev = lines[0].split()[1].split(b':')[1]
         except Exception:
             rev = lines[0].split()[1]
 
@@ -87,9 +86,9 @@ def testUpdateWithRevisionPin(self, develop, src, tempdir):
                 url='%s' % repository,
                 path=os.path.join(src, 'egg'))}
         CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-        assert set(os.listdir(os.path.join(src, 'egg'))) == set(('.hg', 'foo'))
+        assert set(os.listdir(os.path.join(src, 'egg'))) == {'.hg', 'foo'}
         CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-        assert set(os.listdir(os.path.join(src, 'egg'))) == set(('.hg', 'foo'))
+        assert set(os.listdir(os.path.join(src, 'egg'))) == {'.hg', 'foo'}
 
     def testUpdateWithBranch(self, develop, src, tempdir):
         from mr.developer.commands import CmdCheckout
@@ -113,9 +112,9 @@ def testUpdateWithBranch(self, develop, src, tempdir):
                 url='%s' % repository,
                 path=os.path.join(src, 'egg'))}
         CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-        assert set(os.listdir(os.path.join(src, 'egg'))) == set(('.hg', 'foo'))
+        assert set(os.listdir(os.path.join(src, 'egg'))) == {'.hg', 'foo'}
         CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-        assert set(os.listdir(os.path.join(src, 'egg'))) == set(('.hg', 'foo'))
+        assert set(os.listdir(os.path.join(src, 'egg'))) == {'.hg', 'foo'}
 
     def testUpdateRaiseWithRevAndBranch(self, develop, src, tempdir):
         from mr.developer.commands import CmdCheckout
@@ -133,7 +132,7 @@ def testUpdateRaiseWithRevAndBranch(self, develop, src, tempdir):
         lines = process.check_call("hg log %s" % foo, echo=False)
         try:
             # XXX older version
-            rev = lines[0].split()[1].split(b(':'))[1]
+            rev = lines[0].split()[1].split(b':')[1]
         except Exception:
             rev = lines[0].split()[1]
 
diff --git a/src/mr/developer/tests/test_svn.py b/src/mr/developer/tests/test_svn.py
index 242cebe..0432bd5 100644
--- a/src/mr/developer/tests/test_svn.py
+++ b/src/mr/developer/tests/test_svn.py
@@ -1,4 +1,4 @@
-from mock import patch
+from unittest.mock import patch
 from mr.developer.extension import Source
 from mr.developer.tests.utils import Process
 import os
@@ -19,7 +19,7 @@ def testUpdateWithoutRevisionPin(self, develop, src, tempdir):
         process.check_call("svnadmin create %s" % repository)
         checkout = tempdir['checkout']
         process.check_call(
-            "svn checkout file://%s %s" % (repository, checkout),
+            f"svn checkout file://{repository} {checkout}",
             echo=False)
         foo = checkout['foo']
         foo.create_file('foo')
@@ -39,9 +39,9 @@ def testUpdateWithoutRevisionPin(self, develop, src, tempdir):
         log = _log.__enter__()
         try:
             CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('.svn', 'bar', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'.svn', 'bar', 'foo'}
             CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-            assert set(os.listdir(src['egg'])) == set(('.svn', 'bar', 'foo'))
+            assert set(os.listdir(src['egg'])) == {'.svn', 'bar', 'foo'}
             assert log.method_calls == [
                 ('info', ("Checked out 'egg' with subversion.",), {}),
                 ('info', ("Updated 'egg' with subversion.",), {})]
@@ -56,7 +56,7 @@ def testUpdateWithRevisionPin(self, develop, src, tempdir):
         process.check_call("svnadmin create %s" % repository)
         checkout = tempdir['checkout']
         process.check_call(
-            "svn checkout file://%s %s" % (repository, checkout),
+            f"svn checkout file://{repository} {checkout}",
             echo=False)
         foo = checkout['foo']
         foo.create_file('foo')
@@ -73,6 +73,6 @@ def testUpdateWithRevisionPin(self, develop, src, tempdir):
                 url='file://%s@1' % repository,
                 path=src['egg'])}
         CmdCheckout(develop)(develop.parser.parse_args(['co', 'egg']))
-        assert set(os.listdir(src['egg'])) == set(('.svn', 'foo'))
+        assert set(os.listdir(src['egg'])) == {'.svn', 'foo'}
         CmdUpdate(develop)(develop.parser.parse_args(['up', 'egg']))
-        assert set(os.listdir(src['egg'])) == set(('.svn', 'foo'))
+        assert set(os.listdir(src['egg'])) == {'.svn', 'foo'}
diff --git a/src/mr/developer/tests/utils.py b/src/mr/developer/tests/utils.py
index a64f175..f7c8c8d 100644
--- a/src/mr/developer/tests/utils.py
+++ b/src/mr/developer/tests/utils.py
@@ -1,5 +1,4 @@
 from subprocess import Popen, PIPE
-from mr.developer.compat import s
 import os
 import sys
 import threading
@@ -22,7 +21,7 @@ def tee(process, filter_func):
         if line:
             stripped_line = line.rstrip()
             if filter_func(stripped_line):
-                sys.stdout.write(s(line))
+                sys.stdout.write(line.decode('utf-8'))
             lines.append(stripped_line)
         elif process.poll() is not None:
             break
@@ -41,12 +40,12 @@ def tee2(process, filter_func):
         if line:
             stripped_line = line.rstrip()
             if filter_func(stripped_line):
-                sys.stderr.write(s(line))
+                sys.stderr.write(line.decode('utf-8'))
         elif process.poll() is not None:
             break
 
 
-class background_thread(object):
+class background_thread:
     """Context manager to start and stop a background thread."""
 
     def __init__(self, target, args):
@@ -105,21 +104,21 @@ def popen(cmd, echo=True, echo2=True, env=None, cwd=None):
     return process.returncode, lines
 
 
-class On(object):
+class On:
     """A tee filter printing all lines."""
 
     def __call__(self, line):
         return True
 
 
-class Off(object):
+class Off:
     """A tee filter suppressing all lines."""
 
     def __call__(self, line):
         return False
 
 
-class Process(object):
+class Process:
     """Process related functions using the tee module."""
 
     def __init__(self, quiet=False, env=None, cwd=None):
@@ -139,7 +138,7 @@ def check_call(self, cmd, **kw):
         return lines
 
 
-class MockConfig(object):
+class MockConfig:
     def __init__(self):
         self.buildout_args = []
         self.develop = {}
@@ -149,7 +148,7 @@ def save(self):
         pass
 
 
-class MockDevelop(object):
+class MockDevelop:
     def __init__(self):
         from mr.developer.develop import ArgumentParser
         self.always_accept_server_certificate = True
@@ -163,7 +162,7 @@ def __init__(self):
         self.threads = 1
 
 
-class GitRepo(object):
+class GitRepo:
     def __init__(self, base):
         self.base = base
         self.url = 'file:///%s' % self.base
@@ -189,7 +188,7 @@ def add_file(self, fname, msg=None):
         self("git add %s" % repo_file, echo=False)
         if msg is None:
             msg = fname
-        self("git commit %s -m %s" % (repo_file, msg), echo=False)
+        self(f"git commit {repo_file} -m {msg}", echo=False)
 
     def add_dir(self, dirname):
         repo_dir = self.base[dirname]
@@ -197,7 +196,7 @@ def add_dir(self, dirname):
 
     def add_submodule(self, submodule, submodule_name):
         assert isinstance(submodule, GitRepo)
-        self("git -c protocol.file.allow=always submodule add %s %s" % (submodule.url, submodule_name))
+        self(f"git -c protocol.file.allow=always submodule add {submodule.url} {submodule_name}")
         self("git add .gitmodules")
         self("git add %s" % submodule_name)
         self("git commit -m 'Add submodule %s'" % submodule_name)
diff --git a/tox.ini b/tox.ini
index 98f9e4a..c402cdf 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py27-configparser,py34,py35,py36,py37,py38,py39,py310,py311,py312,py313,flake8
+envlist = py310,py311,py312,py313,py314,py315,flake8
 
 [base]
 deps =