Thanks Carl Meyer and Tim Graham for the reviews.

Thanks Thomas Recouvreux for the report and Tim Graham for the tests and
review.

This fixes a regression with runtests.py --reverse after
bd53db5e

We need to avoid leaking model registration in the default AdminSite.

Thanks Luis Del Giudice for the report, and Aymeric Augustin and Markus
Holtermann for the reviews.

Arguments shown in example code (signal, sender, instance) appeared to
be the incorrect positional arguments for a post_save signal (which
might start as: sender, instance, created), as documented:
​https://docs.djangoproject.com/en/1.8/ref/signals/#post-save

Fixed in master by b68212f5.

Forwardport of 290c9d66 from stable/1.8.x

Fixed situation when parent abstract model declares related_name='+',
and child models had an invalid queryset.

Thanks Tim Graham for the review.

When the query's model had a self-referential foreign key, the
compiler.get_group_by() code incorrectly used the self-referential
foreign key's column (for example parent_id) as GROUP BY clause
when it should have used the model's primary key column (id).

This code added in 45e04993
is no longer necessary to pass the model_formsets_regress tests
as of 5e2c4a4b.

With the introduction of multiple template engines these exceptions are no
longer DTL-specific. It makes more sense for them to be moved out of
DTL-related modules.

Thanks Michael Diener for the report and sample data, and Tim Graham
for the review.