Django doesn't make it easy to write unit tests that have their own

custom models. The test runner has to add an app with a models.py file

to INSTALLED_APPS, and the models have to live somewhere within that

directory. This is a lot of work, and it's hard to keep things clean

this way.
This introduces a new mixin that can be used to allow a file containing

unit tests to define custom models. The classes that need to use the

models simply define the models within the file, use the mixin, and then

operate on them.
The mixin handles the hard work of sticking the module in

INSTALLED_APPS, loading the module, and also creating a fake 'models'

module to satisfy Django's requirements.

Made use of this in a test suite. The models were synced to the database,

and I was able to test against them.