Update django_extensions to 2.2.6

[pyup-bot]

This PR updates django_extensions from 2.2.1 to 2.2.6.

Changelog

### 2.2.6 ``` ----- 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 ``` ### 2.2.5 ``` ----- Changes: - Improvement: travis, add Python 3.8 - Improvement: setup.py, update classifiers ``` ### 2.2.4 ``` ----- Changes: - Improvement: RandomCharField, Support unique_together - Improvement: export_emails, add settings for overriding queryset fields, order_by and the full_name function ``` ### 2.2.3 ``` ----- Changes: - Fix: admin widgets, fix import of static template tag (part 2) ``` ### 2.2.2 ``` ----- Changes: - Fix: autoslugfield, find unique method overrideable - Fix: notes, do not replace dot in template dirs - Fix: admin widgets, fix import of static template tag - Improvement: print_user_for_session, use session backend - Improvement: sqlcreate, postgis support - Improvement: graph_models, permit combination of includes and excludes - Improvement: Adds missing GIS engine to DEFAULT_MYSQL_ENGINES - Improvement: sqldiff, use lowercase field names in MySQL - Improvement: sqldiff, mysql code could duplicate AUTO_INCREMENT and UNSIGNED statements ```

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 #587