[1.7.x] Fixed Python 3.4 test failure.

Backport of 45ef4baf5c from master
[1.7.x] Fixed #22029 -- Removed obsolete advice on registering migrate/syncdb signal handlers.

All signals should now be registered in AppConfig.ready().

Thanks un33k for the report.

Backport of 5233b36693 from master
[1.7.x] Fixed the PostGIS circular imports caused by 1506c71a95.

Thanks to @loic for the help and @timgraham for the review.

refs #12030.

Backport of b9e50e4774 from master
[1.7.x] Add a useful stacklevel to some RemovedInDjango19Warnings

Backport of b077ba7ac1 from master
[1.7.x] Fixed a deprecation warning on Python 3.

Backport of c19bbefca2 from master
[1.7.x] Skipped a test that errors rather than marked it as an expectedFailure.

The test throws an error which Python 3.4 doesn't seem to catch as an
expectedFailure.

refs 7476d96f83a004d674244aeb7a66289035427396

Backport of c170c3761b from master
[1.7.x] Fixed #21941 -- Documented the kwargs param of django.conf.urls.url().

Thanks cjerdonek for the report.

Backport of a779757706 from master
[1.7.x] Added Python 3.4 support notes.

Backport of 306deab2c7 from master
[1.7.x] Skipped JavascriptI18nTests if Firefox isn't properly configured.

Code borrowed from django.contrib.admin.tests. Without this, the class can
throw an exception with something like "The browser appears to have exited
before we could connect. The output was: Error: no display specified"

Backport of e2ac0203d9 from master