Drop support for Python 3.6 & 3.7.

[Mariusz Felisiak]

Django 3.2 LTS, supported until April 2024, is the last version to support:

• Python 3.6 (end of life: December 2021)
• Python 3.7 (end of life: June 2023)

See ​our policy about Python version support and discussions regarding the Python version support policy:

• ​https://groups.google.com/forum/#!topic/django-developers/YDJwI7uvgxU/discussion
• ​https://groups.google.com/forum/#!msg/django-developers/ezUpskYAcyo/discussion

[Claude Paroz]

With my usual conservative hat on, I'd plead to not drop Python 3.7 support too soon. It's still widely used in stable systems (namely Debian) and asking contributors running those systems to install a Python version "by hand" to contribute to Django master branch is not friendly at all.

[Mariusz Felisiak]

Replying to Claude Paroz:

With my usual conservative hat on, I'd plead to not drop Python 3.7 support too soon. It's still widely used in stable systems (namely Debian) and asking contributors running those systems to install a Python version "by hand" to contribute to Django master branch is not friendly at all.

I understand your concerns, but there's not consensus to change the policy on the mailing list. Also, if not in Django 4.0 then we will need to support Python 3.7 to Django 4.2 LTS (end of life April 2026), so 2 more years, and almost 3 years after the last Python 3.7 release.

[Claude Paroz]

I know my practice (using latest released Django on as-much-stable-as-possible systems) is not on the majority side, so you'll never find a consensus to change the policy.

[GitHub <noreply@…>]

In 88e972e4:

Fixed #32265, Refs #32355 -- Removed unnecessary ServerHandler.handle_error().

ConnectionAbortedError, BrokenPipeError, ConnectionResetError raised
from SocketServer.BaseServer.finish_request() are already suppressed
by wsgiref.handlers.BaseHandler.run() in Python 3.7+, see
​https://github.com/python/cpython/commit/47ffc1a9f6fab1c17cdcc325d4af066317369ed7

[Mariusz Felisiak]

​PR

[Carlton Gibson <carlton@…>]

In ec0ff406:

Fixed #32355 -- Dropped support for Python 3.6 and 3.7

[Carlton Gibson <carlton@…>]

In 4372233e:

Refs #32355 -- Restored PY36 and PY37 version constants.

Partially reverts ec0ff406311de88f4e2a135d784363424fe602aa.

PY36 should be removed when Django 2.2 is EOL.
PY37 should be removed when Django 3.2 is EOL.

Thanks to Tim Graham for the report.

[Mariusz Felisiak <felisiak.mariusz@…>]

In cecdec91:

Refs #32355 -- Corrected comments about Python's _NamespacePath.

_NamespacePath supports indexing in Python 3.8+.

[GitHub <noreply@…>]

In 213850b:

Refs #32355 -- Used addClassCleanup() in tests.

Inspired by Adam Johnson talk on DjangoCon Europe 2021.

[GitHub <noreply@…>]

In faba5b7:

Refs #32355 -- Used addClassCleanup() in SimpleTestCase and SerializeMixin.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 840ad063:

Refs #32355 -- Modernized subprocess.run() calls.

[GitHub <noreply@…>]

In 5bac1719:

Refs #32355 -- Used @functools.lru_cache as a straight decorator.

[GitHub <noreply@…>]

In ca04659:

Refs #32355 -- Bumped required psycopg2 version to 2.8.4.

psycopg2 2.8.4 is the first release to support Python 3.8.

[Mariusz Felisiak <felisiak.mariusz@…>]

In b5f60ef5:

[4.0.x] Refs #32355 -- Bumped required psycopg2 version to 2.8.4.

psycopg2 2.8.4 is the first release to support Python 3.8.
Backport of ca04659b4b3f042c1bc7e557c25ed91e3c56c745 from main

[GitHub <noreply@…>]

In 7346c28:

Refs #32355 -- Removed unnecessary list() calls before reversed() on dictviews.

Dict and dictviews are iterable in reversed insertion order using
reversed() in Python 3.8+.

[GitHub <noreply@…>]

In 7d93299:

Refs #32355 -- Bumped mysqlclient requirement to >= 1.4.3.

mysqlclient 1.4.3 is the first release to support Python 3.8.

[GitHub <noreply@…>]

In 63d1cb0:

Refs #32355 -- Bumped minimum supported versions of 3rd-party packages.

This bumps minimum supported versions of 3rd-party packages to the first
releases to support Python 3.8.

[GitHub <noreply@…>]

In fbe85010:

Refs #32355 -- Bumped required version of sqlparse in setup.cfg.

Follow up to 63d1cb0092f8933a92f471c5150d61140f33882c.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 69a3890c:

[4.2.x] Refs #32355 -- Bumped required version of sqlparse in setup.cfg.

Follow up to 63d1cb0092f8933a92f471c5150d61140f33882c.

Backport of fbe850106b2e4b85f838219cb9e1df95fba6c164 from main.

[GitHub <noreply@…>]

In c74a6fa:

Refs #32355 -- Removed unnecessary getattr() call.

options.test_name_patterns is always defined.

Follow up to ec0ff406311de88f4e2a135d784363424fe602aa.