Update django-extensions to 2.2.8

[pyup-bot]

This PR updates django-extensions from 2.2.5 to 2.2.8.

Changelog

2.2.8

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Changes:
- Locale: zh_Hans, removed as it generated UnicodeDecodeError errors (1478)

2.2.7

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Changes:
- Improvement: shell_plus, 865 always add manage.py basedir to path for notebook kernel
- Improvement: docs, add zh-Hans locale
- Improvement: runserver_plus, fix broken import for werkzeug v1.0.0
- Improvement: runserver_plus, 1461 fix always trying to load StaticFilesHandler
- Improvement: pipchecker, 1471 fix import of PipSession

2.2.6

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Changes:
- Improvement: travis, update pypy and pypy3 versions
- Improvement: shell_plus, ability to print location/traceback besides sql
- Improvement: runserver_plus, ability to print location/traceback besides sql
- Improvement: UniqueFieldMixin, Support Django 2.2 UniqueConstraint.condition
- Improvement: DEFAULT_MYSQL_ENGINES, add mysql.connector.django
- Improvement: shell_plus, allow setting SHELL_PLUS="notebook"
- Improvement: shell_plus, add -c/--command to shell_plus mirroring django's shell command
- Fix: shell_plus, fix postgresql debug wrapper on django 3.0 or higher
- Fix: runserver_plus, fix postgresql debug wrapper on django 3.0 or higher

Links

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

[coveralls]

Coverage remained the same at 96.719% when pulling cf04a9d on pyup-update-django-extensions-2.2.5-to-2.2.8 into 24f2f61 on master.