There were two classes named `StatusCustomManager`: the first is an
actual manager, the second a status model that uses a custom manager.
The latter is renamed to `CustomManagerStatusModel` in this commit.
* add test for reproducing FieldTracker update_fields issue
FieldTracker does not see update_fields changed in tracked model.save() method
* Patch Model.save_base instead of save
This change allows proper capturing update_fields kwarg if is is changed in overridden save() method.
* Add some details about FieldTracker implementation
* Mention FieldTracker behavior change
* - add django 3.0 to the test matrix
- drop six
* add entry in CHANGES
* remove context kwarg
* fix test with DeferredAttribute
* rename StringyDescriptor's name to attname
* Fix flake8
* Drop support for Django 1.11 because the API are not compatibles anymore with Django 3.0
* Try to fix tests.
* Define model for the field mock.
* Simplifies the code.
* Properly mock the field.
* Typo
* Use the new API field name.
* Call it attname
* Grab the field instance from the model.
* Use postgres in travis tests.
* Django 2.0.1 minimum is needed.
* Update Changelog to tell about breaking Django 1.11.
* Update changelog to tell about Django 3.0 support.
* @natim review.
* Add the join manager + tests
* Documentation for join manager
* Use order_by for consistent tests
* Use postgres instead sqlite for tests for better reliability
* Fix coverage
* Drop django 1.8
