Thanks KevinEtienne for the suggestion.

On MySQLdb < 1.2.5, MySQLdb returns None when fetching datetime/time
values with fractional seconds.
See https://github.com/farcepest/MySQLdb1/issues/24

Thanks erik@cederstrand.dk for the report and Tim Graham for the review.

Refs #19716.

Refs #14334

Thanks inglesp for the report.

Thanks CHI Cheng for the report.

Thanks Corey Farwell for the report and Tim Graham for the review.
Thanks also to Inada Naoki for creating and maintaining mysqlclient.

Thanks Bjarkias for the report.

Basically a4737bf6 reapplied.

Thanks gavinwahl for the report.

In some test combinations, having contrib.auth available but not
contrib.contenttypes can produce failures while creating permissions.

Thanks Keryn Knight for the report.

Thanks Naddiseo for the report, Andrew Godwin for guidance,
and Shai Berger for review.

That test might not always execute, but can be executed when the
parent test label is explicitely given.

Thanks dfunckt and Tim Graham.

Previously a RuntimeError was raised every time two models clashed
in the app registry. This prevented reloading a module in a REPL;
while it's not recommended to do so, we decided not to forbid this
use-case by turning the error into a warning.

Thanks @dfunckt and Sergey Pashinin for the initial patches.

Thanks prathik for the report.