BUILD: drop support for python 3.6 (#4701)

Following our support table, we drop python 3.6 support.

Author: ltalirz

.github/workflows/ci-code.yml

@@ -50,7 +50,7 @@ jobs:
       fail-fast: false
       matrix:
         backend: ['django', 'sqlalchemy']
-        python-version: [3.6, 3.8]
+        python-version: [3.7, 3.8]
 
     services:
       postgres:
@@ -110,10 +110,10 @@ jobs:
         .github/workflows/tests.sh
 
     - name: Upload coverage report
-      if: matrix.python-version == 3.6 && github.repository == 'aiidateam/aiida-core'
+      if: matrix.python-version == 3.7 && github.repository == 'aiidateam/aiida-core'
       uses: codecov/codecov-action@v1
       with:
-        name: aiida-pytests-py3.6-${{ matrix.backend }}
+        name: aiida-pytests-py3.7-${{ matrix.backend }}
         flags: ${{ matrix.backend }}
         file: ./coverage.xml
         fail_ci_if_error: false  # don't fail job, if coverage upload fails

.github/workflows/test-install.yml

@@ -126,7 +126,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [3.7, 3.8, 3.9]
         backend: ['django', 'sqlalchemy']
 
     services:

aiida/engine/daemon/runner.py

@@ -22,17 +22,10 @@
 
 async def shutdown_runner(runner: Runner) -> None:
     """Cleanup tasks tied to the service's shutdown."""
-    LOGGER.info('Received signal to shut down the daemon runner')
-
-    try:
-        from asyncio import all_tasks
-        from asyncio import current_task
-    except ImportError:
-        # Necessary for Python 3.6 as `asyncio.all_tasks` and `asyncio.current_task` were introduced in Python 3.7. The
-        # Standalone functions should be used as the classmethods are removed as of Python 3.9.
-        all_tasks = asyncio.Task.all_tasks
-        current_task = asyncio.Task.current_task
+    from asyncio import all_tasks
+    from asyncio import current_task
 
+    LOGGER.info('Received signal to shut down the daemon runner')
     tasks = [task for task in all_tasks() if task is not current_task()]
 
     for task in tasks:

aiida/orm/implementation/django/comments.py

@@ -67,9 +67,7 @@ def store(self):
         if self._dbmodel.dbnode.id is None or self._dbmodel.user.id is None:
             raise exceptions.ModificationNotAllowed('The corresponding node and/or user are not stored')
 
-        # `contextlib.suppress` provides empty context and can be replaced with `contextlib.nullcontext` after we drop
-        # support for python 3.6
-        with suppress_auto_now([(models.DbComment, ['mtime'])]) if self.mtime else contextlib.suppress():
+        with suppress_auto_now([(models.DbComment, ['mtime'])]) if self.mtime else contextlib.nullcontext():
             super().store()
 
     @property

aiida/orm/implementation/django/nodes.py

@@ -201,10 +201,8 @@ def store(self, links=None, with_transaction=True, clean=True):  # pylint: disab
         if clean:
             self.clean_values()
 
-        # `contextlib.suppress` provides empty context and can be replaced with `contextlib.nullcontext` after we drop
-        # support for python 3.6
-        with transaction.atomic() if with_transaction else contextlib.suppress():
-            with suppress_auto_now([(models.DbNode, ['mtime'])]) if self.mtime else contextlib.suppress():
+        with transaction.atomic() if with_transaction else contextlib.nullcontext():
+            with suppress_auto_now([(models.DbNode, ['mtime'])]) if self.mtime else contextlib.nullcontext():
                 # We need to save the node model instance itself first such that it has a pk
                 # that can be used in the foreign keys that will be needed for setting the
                 # attributes and links

docs/source/intro/install_system.rst

@@ -15,7 +15,7 @@ This is the *recommended* installation method to setup AiiDA on a personal lapto
 
    **Install prerequisite services**
 
-      AiiDA is designed to run on `Unix <https://en.wikipedia.org/wiki/Unix>`_ operating systems and requires a `bash <https://en.wikipedia.org/wiki/Bash_(Unix_shell)>`_ or `zsh <https://en.wikipedia.org/wiki/Z_shell>`_ shell, and Python >= 3.6.
+      AiiDA is designed to run on `Unix <https://en.wikipedia.org/wiki/Unix>`_ operating systems and requires a `bash <https://en.wikipedia.org/wiki/Bash_(Unix_shell)>`_ or `zsh <https://en.wikipedia.org/wiki/Z_shell>`_ shell, and Python >= 3.7.
 
    .. tabbed:: Ubuntu
 

environment.yml

@@ -15,7 +15,6 @@ dependencies:
 - click-config-file~=0.6.0
 - click-spinner~=0.1.8
 - click~=7.1
-- dataclasses~=0.7
 - django~=2.2
 - ete3~=3.1
 - python-graphviz~=0.13

pyproject.toml

@@ -76,7 +76,6 @@ envlist = py37-django
 [testenv]
 usedevelop=True
 deps =
-    py36: -rrequirements/requirements-py-3.6.txt
     py37: -rrequirements/requirements-py-3.7.txt
     py38: -rrequirements/requirements-py-3.8.txt
     py39: -rrequirements/requirements-py-3.9.txt
@@ -109,7 +108,6 @@ commands =
 # tip: remove apidocs before using this feature (`cd docs; make clean`)
 description = Build the documentation and launch browser (with live updates)
 deps =
-    py36: -rrequirements/requirements-py-3.6.txt
     py37: -rrequirements/requirements-py-3.7.txt
     py38: -rrequirements/requirements-py-3.8.txt
     py39: -rrequirements/requirements-py-3.9.txt

requirements/requirements-py-3.6.txt

@@ -7,14 +7,13 @@
     "author_email": "developers@aiida.net",
     "description": "AiiDA is a workflow manager for computational science with a strong focus on provenance, performance and extensibility.",
     "include_package_data": true,
-    "python_requires": ">=3.6.1",
+    "python_requires": ">=3.7",
     "classifiers": [
         "Framework :: AiiDA",
         "License :: OSI Approved :: MIT License",
         "Operating System :: POSIX :: Linux",
         "Operating System :: MacOS :: MacOS X",
         "Programming Language :: Python",
-        "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
@@ -30,7 +29,6 @@
         "click-config-file~=0.6.0",
         "click-spinner~=0.1.8",
         "click~=7.1",
-        "dataclasses~=0.7; python_version < '3.7.0'",
         "django~=2.2",
         "ete3~=3.1",
         "graphviz~=0.13",