* Added TEMPLATES setting to tests
* Remove deprecated view-string in URL conf
* Replace 'urls = ...' in test classes with override_settings('ROOT_URLCONF=...')
* Refactor UsingURLPatterns to use override_settings(ROOT_URLCONF=...) style
* Get model managers and names in a version-compatible manner.
* Apply override_settings to a TestCase, not a mixin class
* Use '.callback' property instead of private attributes when inspecting urlpatterns
* Pass 'user' to template explicitly
* Correct sorting of import statements.
* Remove unused TEMPLATE_LOADERS setting, in favor of TEMPLATES.
* Remove code style issue
* BaseFilter test requires a concrete model
* Resolve tox.ini issues
* Resolve isort differences between local and tox environments
