Update django to 2.2.3

[pyup-bot]

This PR updates django from 2.2.2 to 2.2.3.

Changelog

### 2.2.3 ``` ========================== *Expected July 1, 2019* Django 2.2.3 fixes several bugs in 2.2.2. Also, the latest string translations from Transifex are incorporated. Bugfixes ======== * Fixed a regression in Django 2.2 where :class:`~django.db.models.Avg`, :class:`~django.db.models.StdDev`, and :class:`~django.db.models.Variance` crash with ``filter`` argument (:ticket:`30542`). * Fixed a regression in Django 2.2.2 where auto-reloader crashes with ``AttributeError``, e.g. when using ``ipdb`` (:ticket:`30588`). ========================== ```

Links

- PyPI: https://pypi.org/project/django - Changelog: https://pyup.io/changelogs/django/ - Homepage: https://www.djangoproject.com/

[coveralls]

Pull Request Test Coverage Report for Build 1162

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.275%

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Totals
Change from base Build 1157:	0.0%
Covered Lines:	2191
Relevant Lines:	2207

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💛 - Coveralls

[pyup-bot]

Closing this in favor of #278