Update django-extensions to 3.1.1

[pyup-bot]

This PR updates django-extensions from 3.0.9 to 3.1.1.

Changelog

3.1.1

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Changes:
- Improvement: graph_models, add option --app-labels
- Improvement: shell_plus, update shell_plus for jupyterlab 3
- Improvement: tests, add Python 3.9

3.1.0

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Changes:
- Improvement: pipchecker, sleep 60s if pypi raises a fault
- Improvement: add django_zero_downtime_migrations to list of supported postgresql engines
- Improvement: use list of supported database engines from settings for all database commands
- Improvement: reset_db, documentation
- Fix: tests, Python 3.9 fixes for some tests
- Fix: runserver_plus, parsing of RUNSERVER_PLUS_EXTRA_FILES

Links

• PyPI: https://pypi.org/project/django-extensions
• Changelog: https://pyup.io/changelogs/django-extensions/
• Repo: http://github.com/django-extensions/django-extensions

[pyup-bot]

Closing this in favor of #1672