Update pytest-django to 3.9.0

[pyup-bot]

This PR updates pytest-django from 3.8.0 to 3.9.0.

Changelog

3.9.0

-------------------

Improvements
^^^^^^^^^^^^

* Improve test ordering with Django test classes (830)

* Remove import of pkg_resources for parsing pytest version (performance) (826)

Bugfixes
^^^^^^^^

* Work around unittest issue with pytest 5.4.{0,1} (825)

* Don't break --failed-first when re-ordering tests (819, 820)

* pytest_addoption: use `group.addoption` (833)

Misc
^^^^

* Remove Django version from --nomigrations heading (822)

* docs: changelog: prefix headers with v for permalink anchors

* changelog: add custom/fixed anchor for last version

* setup.py: add Changelog to project_urls

Links

• PyPI: https://pypi.org/project/pytest-django
• Changelog: https://pyup.io/changelogs/pytest-django/
• Docs: https://pytest-django.readthedocs.io/