feat: Support Django 4.1

[adamchainz]

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[coveralls]

Coverage increased (+0.01%) to 91.572% when pulling 798e15f on adamchainz:django_4.1 into 6315e25 on pennersr:master.

[adamchainz]

This and similar changes are all to deal with the test change to assertFormError(). Without it, the test run records warnings from Django like:

/.../lib/python3.10/site-packages/django/test/testcases.py:279: RemovedInDjango50Warning: Passing response to assertFormError() is deprecated. Use the form object directly: assertFormError(response.context['form'], None, ...)

Using a branch on django.VERSION seems to be the most elegant way to handle the two different calling formats. If you use django-upgrade in the future, when dropping <4.1 support, it can rewrite the code to leave only the "new way of doing thigns" with its versioned blocks fixer.

[adamchainz]

This settings change is required to deal with this warning from Django 4.0+:

/.../lib/python3.10/site-packages/django/conf/__init__.py:214: RemovedInDjango50Warning: The default value of USE_TZ will change from False to True in Django 5.0. Set USE_TZ to False in your project settings if you want to keep the current default behavior.
  warnings.warn(

It seems that nothing in the test suite is affected by the change - I can't spot any more warnings and there aren't any errors.

[adamchainz]

I tried to match changes to github actions to the Django 4.0 commit: f02dcfa