Thanks Russell Keith-Magee and Tim Graham for reviews.

This reverts commit 80f4487d temporarily, because that commit prevented
the djangoproject.com server from building the docs, because it still
uses Python 2.6.

This improves pickling speed in prelease versions of Django; refs #21430.

Thanks flisky for the report.

Thanks jorgecarleitao and mmardini for reviews.

Thanks to jonathanmorgan for the report and initial patch.

Thanks to Chris Beaven.

Fixed #13711 -- Model check added to ensure that auto-generated column name is within limits of the database.

Thanks russellm for report and Tim Graham for review.

Made url syntax consistent in tutorial; refs #22218.

Fixed #22577: Python 3 broke on non-module migrations directory

Thanks jorgecarleitao for the suggestion.

Thanks maxi for the suggestion.

refs #22170.

Moved contenttypes tests to allow them to run correctly in the presence of
migrations. refs #22170.

This inspects the migration operation, and if it is not in the
django.db.migrations module, it adds the relevant imports to the
migration writer and uses the correct class name.

refs #22170.

Without this, we're unable to add actual migrations for the app.