Reverted test changes in a7a7ecd2 and
e43ea36b (refs #27025).

Thanks Yuriy Korobko for the initial patch and Tobias McNulty for review.

(Fixed #23604 in 2014 and was not added before.)

Thanks samuller for the report and initial patch.

'CASCADE' is an undocumented no-op in MySQL, so to avoid confusion Django no longer outputs it.

This is a security fix.

This is a security fix.

Thanks Tim Graham for the initial patch.

This allows bringing back the behavior of Django < 1.7.

Also fixed the check for the app registry being ready in
AppConfig.get_model(s), which was inconsistent with the equivalent check in
Apps.get_model(s). That part is a backwards-incompatible change.