Fix GitHub Actions configuration

[johnthagen]

Bug Fix

Description

The GitHub Actions tox configuration was misconfigured such that no unit tests were actually running.

This was due in part to non-standard tox configuration conventions py3.6 vs py36. This PR uses the standard Python versioning that is available by default in tox.

• https://tox.wiki/en/latest/config.html#tox-environments

Regression in

• 2d7151f
• Add support for Django 4.0 #408

Also remove deprecated import that caused failure under Python 3.10

Why should this be added

Currently no unit tests are running on CI

[johnthagen]

This is a legitimate 3.10 testing failure:

    File "/home/runner/work/django-dbbackup/django-dbbackup/dbbackup/tests/testapp/urls.py", line 8, in <module>
      from django.conf.urls import include, url
  ImportError: cannot import name 'url' from 'django.conf.urls' (/home/runner/work/django-dbbackup/django-dbbackup/.tox/py310-django40/lib/python3.10/site-packages/django/conf/urls/__init__.py)

[Archmonger]

@johnthagen As quick note, all Jazzband members have the ability to merge PRs.

Being a project lead only provides the ability to create releases on PyPI.

Also, jezdez has added me as a project lead according to https://jazzband.co/projects/django-dbbackup