translation.override() context manager doesn't return to deactivated state when there's no activated language

[David Nelson Adamec]

From a shell, I'm able to do the following:

In [1]: from django.utils import translation

In [2]: translation.get_language()

In [3]: with translation.override('fr'):
   ...:     pass
   ...:

In [4]: translation.get_language()
Out[4]: 'fr'

override usually reverts to the previous language upon leaving the context manager, so this behavior seems unexpected.

This is new in Django 1.8: before, get_language() returned the default language, so the default language would be activated after override finished. Now get_language() returns None when there is no active catalog, so override attempts to activate None, which has no effect.

[Tim Graham]

I'm not a translation expert, but that does seem incorrect.

[Tim Graham]

Seems like a candidate for backport if you like.

[Claude Paroz <claude@…>]

In 9324935c:

Fixed #25295 -- Restored 'no active translation' after language override

Thanks David Nelson Adamec for the report and Tim Graham for the review.

[Claude Paroz <claude@…>]

In c177d069:

[1.8.x] Fixed #25295 -- Restored 'no active translation' after language override

Thanks David Nelson Adamec for the report and Tim Graham for the review.
Backport of 9324935c3 from master.