This is the result of Christopher Medrela's 2013 Summer of Code project.
Thanks also to Preston Holmes, Tim Graham, Anssi Kääriäinen, Florian
Apolloner, and Alex Gaynor for review notes along the way.
Also: Fixes #8579, fixes #3055, fixes #19844.
It doesn't work as one might expect on a certain database backend where
autocommits_when_autocommit_is_off = True. That backend happens to be
popular for running tests.
The failure was caused by generating the same warning from two tests.
The second time the same warning was raised it was swallowed by the
"once" simplefilter of warnings.
If the fixture doesn't exist, loaddata will output a warning.
The fixture named "initial_data" is exceptional though; if it
doesn't exist, the warning is not emitted. This allows syncdb and
flush management commands to attempt to load it without causing
spurious warnings.
Thanks to Derega, ptone, dirigeant and d1ffuz0r for contributions
to the ticket.
