diff --git a/README.rst b/README.rst
index 687ba6713..7db26c884 100644
--- a/README.rst
+++ b/README.rst
@@ -73,6 +73,7 @@ What's New?
 in development
 ^^^^^^^^^^^^^^
 
+* When option ``-W/--warnings-as-errors`` is used, pydoctor exits with code 3 when it issues any warning.
 * Hide sidebar element title when all items under it are private.
 * Allow suppressing the footer's buildtime altogether with option ``--buildtime=no``.
 * Add project version on each HTML page.
diff --git a/pydoctor/_configparser.py b/pydoctor/_configparser.py
index e38d697ad..842475646 100644
--- a/pydoctor/_configparser.py
+++ b/pydoctor/_configparser.py
@@ -31,7 +31,6 @@
 import functools
 import configparser
 from ast import literal_eval
-import warnings
 
 from configargparse import ConfigFileParserException, ConfigFileParser, ArgumentParser
 
@@ -435,7 +434,8 @@ def parse(self, stream:TextIO) -> Dict[str, Any]:
             action = known_config_keys.get(key)
             if not action:
                 # Warn "no such config option"
-                warnings.warn(f"No such config option: {key!r}")
+                from pydoctor.utils import warn
+                warn(f"No such config option: {key!r}")
                 # Remove option
             else:
                 new_data[key] = value
diff --git a/pydoctor/driver.py b/pydoctor/driver.py
index a9a10c797..8d53393b3 100644
--- a/pydoctor/driver.py
+++ b/pydoctor/driver.py
@@ -8,7 +8,7 @@
 from pathlib import Path
 
 from pydoctor.options import Options, BUILDTIME_FORMAT, FALSE_VALUES
-from pydoctor.utils import error
+from pydoctor.utils import error, warned
 from pydoctor import model
 from pydoctor.templatewriter import IWriter, TemplateLookup, TemplateError
 from pydoctor.sphinx import SphinxInventoryWriter, prepareCache
@@ -188,7 +188,7 @@ def p(msg: str) -> None:
         elif any(system.parse_errors.values()):
             exitcode = 2
 
-        if system.violations and options.warnings_as_errors:
+        if options.warnings_as_errors and (system.violations or warned()):
             # Update exit code if the run has produced warnings.
             exitcode = 3
 
diff --git a/pydoctor/epydoc/sre_parse36.py b/pydoctor/epydoc/sre_parse36.py
index f3c7b81fb..c6f239a44 100644
--- a/pydoctor/epydoc/sre_parse36.py
+++ b/pydoctor/epydoc/sre_parse36.py
@@ -796,14 +796,8 @@ def _parse(source, state, verbose, nested, first=False):
                     flags = _parse_flags(source, state, char)
                     if flags is None:  # global flags
                         if not first or subpattern:
-                            import warnings
-                            warnings.warn(
-                                'Flags not at the start of the expression %r%s' % (
-                                    source.string[:20],  # truncate long regexes
-                                    ' (truncated)' if len(source.string) > 20 else '',
-                                ),
-                                DeprecationWarning, stacklevel=nested + 6
-                            )
+                            # changed: we don't trigger deprecated warning here
+                            pass
                         if (state.flags & SRE_FLAG_VERBOSE) and not verbose:
                             raise Verbose
                         continue
@@ -1008,9 +1002,8 @@ def addgroup(index, pos):
                     this = chr(ESCAPES[this][1])
                 except KeyError:
                     if c in ASCIILETTERS:
-                        import warnings
-                        warnings.warn('bad escape %s' % this,
-                                      DeprecationWarning, stacklevel=4)
+                        # changed: we don't trigger deprecated warning here
+                        pass
                 lappend(this)
         else:
             lappend(this)
diff --git a/pydoctor/options.py b/pydoctor/options.py
index a8db6d1ea..2cf0e1b7e 100644
--- a/pydoctor/options.py
+++ b/pydoctor/options.py
@@ -5,7 +5,6 @@
 
 import re
 from typing import NamedTuple, Sequence, List, Optional, Type, Tuple, TYPE_CHECKING
-import sys
 import functools
 from pathlib import Path
 from argparse import SUPPRESS, Namespace
@@ -291,9 +290,9 @@ def _warn_deprecated_options(options: Namespace) -> None:
     Check the CLI options and warn on deprecated options.
     """
     if options.enable_intersphinx_cache_deprecated:
-        print("The --enable-intersphinx-cache option is deprecated; "
-              "the cache is now enabled by default.",
-              file=sys.stderr, flush=True)
+        from pydoctor.utils import warn
+        warn("The --enable-intersphinx-cache option is deprecated; "
+              "the cache is now enabled by default.")
 
 # CONVERTERS
 
diff --git a/pydoctor/templatewriter/__init__.py b/pydoctor/templatewriter/__init__.py
index 4cdddb357..30d7882cd 100644
--- a/pydoctor/templatewriter/__init__.py
+++ b/pydoctor/templatewriter/__init__.py
@@ -10,7 +10,6 @@ def runtime_checkable(f):
         return f
 import abc
 from pathlib import Path, PurePath
-import warnings
 from xml.dom import minidom
 
 # Newer APIs from importlib_resources should arrive to stdlib importlib.resources in Python 3.9.
@@ -241,7 +240,8 @@ def _extract_version(dom: minidom.Document, template_name: str) -> int:
             meta.parentNode.removeChild(meta)
 
             if not meta.hasAttribute("content"):
-                warnings.warn(f"Could not read '{template_name}' template version: "
+                from pydoctor.utils import warn
+                warn(f"Could not read '{template_name}' template version: "
                     f"the 'content' attribute is missing")
                 continue
 
@@ -250,7 +250,8 @@ def _extract_version(dom: minidom.Document, template_name: str) -> int:
             try:
                 version = int(version_str)
             except ValueError:
-                warnings.warn(f"Could not read '{template_name}' template version: "
+                from pydoctor.utils import warn
+                warn(f"Could not read '{template_name}' template version: "
                         "the 'content' attribute must be an integer")
             else:
                 break
@@ -295,7 +296,8 @@ def _add_overriding_html_template(self, template: HtmlTemplate, current_template
         template_version = template.version
         if default_version != -1 and template_version != -1:
             if template_version < default_version:
-                warnings.warn(f"Your custom template '{template.name}' is out of date, "
+                from pydoctor.utils import warn
+                warn(f"Your custom template '{template.name}' is out of date, "
                                 "information might be missing. "
                                 "Latest templates are available to download from our github." )
             elif template_version > default_version:
diff --git a/pydoctor/templatewriter/util.py b/pydoctor/templatewriter/util.py
index 95699854c..635a13cf6 100644
--- a/pydoctor/templatewriter/util.py
+++ b/pydoctor/templatewriter/util.py
@@ -1,7 +1,6 @@
 """Miscellaneous utilities for the HTML writer."""
 from __future__ import annotations
 
-import warnings
 from typing import (Any, Callable, Dict, Generic, Iterable, Iterator, List, Mapping, 
                     Optional, MutableMapping, Tuple, TypeVar, Union, Sequence, TYPE_CHECKING)
 from pydoctor import epydoc2stan
@@ -164,7 +163,8 @@ def inherited_members(cls: model.Class) -> List[model.Documentable]:
 
 def templatefile(filename: str) -> None:
     """Deprecated: can be removed once Twisted stops patching this."""
-    warnings.warn("pydoctor.templatewriter.util.templatefile() "
+    from pydoctor.utils import warn
+    warn("pydoctor.templatewriter.util.templatefile() "
         "is deprecated and returns None. It will be remove in future versions. "
         "Please use the templating system.")
     return None
diff --git a/pydoctor/test/test_commandline.py b/pydoctor/test/test_commandline.py
index dae6aa353..6606e548f 100644
--- a/pydoctor/test/test_commandline.py
+++ b/pydoctor/test/test_commandline.py
@@ -3,6 +3,7 @@
 from pathlib import Path
 import re
 import sys
+import warnings
 import logging
 
 import pytest
@@ -346,6 +347,65 @@ def test_html_ids_dont_look_like_python_names(tmp_path: Path) -> None:
         else:
             assert re.findall(r'id="[a-z]+"', text, re.IGNORECASE) == [], text
 
+def test_no_such_option_exits_code0(tmp_path: Path) -> None:
+    """
+    When no such option is used in the config file it just ignores it and
+    continues normally, whith a warning message printed to stderr.
+    """
+    
+    tmp_path.mkdir(parents=True, exist_ok=True)
+    conf_file = (tmp_path / "pydoctor_temp_conf")
+    with conf_file.open('w') as f:
+        f.write("[pydoctor]\nno-such-option = somevalue\n")
+
+    with warnings.catch_warnings(record=True) as w:
+        exit_code = driver.main(args=[
+            '--config', str(conf_file),
+            '--html-output', str(tmp_path / 'output'),
+            'pydoctor/test/testpackages/basic/'
+            ])
+    
+    assert exit_code == 0
+    assert [str(warn.message) for warn in w] == ["No such config option: 'no-such-option'"]
+
+def test_warnings_as_errors_configured_from_config_file_no_such_option_exits_code3(tmp_path: Path) -> None:
+    """
+    When `warnings-as-errors = true` is used it returns 3 as exit code when there are warnings.
+
+    We demonstrate this using a non existing configuration keyword
+    """
+    
+    tmp_path.mkdir(parents=True, exist_ok=True)
+    conf_file = (tmp_path / "pydoctor_temp_conf")
+    with conf_file.open('w') as f:
+        f.write("[pydoctor]\nno-such-option = somevalue\nwarnings-as-errors = true\n")
+
+    with warnings.catch_warnings(record=True) as w:
+        exit_code = driver.main(args=[
+            '--config', str(conf_file),
+            '--html-output', str(tmp_path / 'output'),
+            'pydoctor/test/testpackages/basic/'
+            ])
+
+    assert exit_code == 3
+    assert [str(warn.message) for warn in w] == ["No such config option: 'no-such-option'"]
+
+def test_warnings_as_errors_configured_from_cli_option_no_such_option_exits_code3(tmp_path: Path) -> None:
+    """
+    When `-W` is used it returns 3 as exit code when there are warnings.
+
+    We demonstrate this using deprecated option --enable-intersphinx-cache. 
+    """
+    with warnings.catch_warnings(record=True) as w:
+        exit_code = driver.main(args=[
+            '-W', '--enable-intersphinx-cache', 
+            '--html-output', str(tmp_path / 'output'),
+            'pydoctor/test/testpackages/basic/'
+            ])
+
+    assert exit_code == 3
+    assert [str(warn.message) for warn in w] == ["The --enable-intersphinx-cache option is deprecated; the cache is now enabled by default."]
+
 def test_invalid_intersphinx_url_exits_code2(tmp_path: Path, capsys: CapSys, caplog: CapLog) -> None:
     caplog.set_level(logging.ERROR)
     # test for issue https://github.com/twisted/pydoctor/issues/751
diff --git a/pydoctor/utils.py b/pydoctor/utils.py
index 6d80387c6..37ffff698 100644
--- a/pydoctor/utils.py
+++ b/pydoctor/utils.py
@@ -4,6 +4,7 @@
 from pathlib import Path
 import sys
 import functools
+import contextvars
 from typing import Any, Type, TypeVar, Tuple, Union, cast, TYPE_CHECKING
 
 if TYPE_CHECKING:
@@ -103,3 +104,24 @@ class NewPartialCls(cls):
         __class__ = cls
     assert isinstance(NewPartialCls, type)
     return NewPartialCls
+
+class PydoctorWarning(UserWarning):
+    """
+    Base class for all warnings emitted by pydoctor thru the L{warnings} module.
+    """
+
+_warned = contextvars.ContextVar('warned', default=False)
+
+def warn(msg: str) -> None:
+    """
+    Emit a pydoctor warning message.
+    """
+    import warnings
+    warnings.warn(msg, category=PydoctorWarning)
+    _warned.set(True)
+
+def warned() -> bool:
+    """
+    Return whether any pydoctor warning has been emitted.
+    """
+    return _warned.get()
\ No newline at end of file
diff --git a/setup.cfg b/setup.cfg
index 9114233e8..4a1de32f2 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -111,6 +111,7 @@ xfail_strict = true
 filterwarnings =
     default::urllib3.exceptions.NotOpenSSLWarning
     error
+    default::pydoctor.utils.PydoctorWarning
     
 [tool:pydoctor]
 intersphinx =