The unit test code makes use of a handful of utility functions, which

handle things like replacing app labels and model names for a batch of

models, populating the database with models, executing SQL, generating

index names to test against for different versions of Django, and more.

Most of this code was pretty old and undocumented, and some of it turned

out to be unnecessary.
This change makes some big cleanups to this code. A whole lot of

functions have been removed (either outright due to no longer being

used, or rolled up into the test case or other code that needed them).

Other functions had unused parameters or logic removed. The remaining

ones received some sizable documentation improvements, helping to make

the code more understandable and maintainable.
In the process, this has been made a bit more Python 3-compatible,

switching to Unicode strings and the six module (though at the moment,

this has not been tested on Python 3).

Unit tests pass on all supported versions of Django.