Thanks to Preston Timmons for the bulk of the work on the patch, especially
updating Django's own test suite to comply with the requirements of the new
runner. Thanks also to Jannis Leidel and Mahdi Yusuf for earlier work on the
patch and the discovery runner.
Refs #11077, #17032, and #18670.
The OGRInspectTest.test_time_field does still not succeed with these
databases (even when removing the postgis guard), but at least it's now
possible to setup a datasource.