Fixed #20194 -- Adds generators support for email backends that do not support it.

Patch from Lukasz Balcerzak.

Thanks abeld for the suggestion.

Additionaly added pickled=None initially and check for none before
returning in get

Django 1.7 will loudly warn when widget attributes are assigned
boolean values. In Django 1.8, False will mean attribute is not
present while True will mean attribute present without value.
Refs #20684.

Thanks Marc Tamlyn and Tim Graham for the review.

Thanks jtiai for the suggestion.

Thanks astorije@ for the report.

fixed grammar

Thanks simonpercivall.

Thanks semenov and pegler.

Thanks littlepig for the report.

Thanks timmolendijk, jdunck, vijay_shanker, and loic84.

Thanks rene@ for the suggestion.

The regression was introduced by 2c4fe761. refs #20593.

Thanks michel@ for the suggestion.

Thanks Baptiste Mispelon for the suggestion.

So as syntax errors in po files don't go unnoticed. Refs #20695.

Thanks garrison for the suggestion.

Fix "semicolon" in form docs

The module still exists for whoever uses it in its current state, but it
isn't imported by Django anywhere.

One import per line please! Refs #20680.

Refs #20680.

Silenced warnings caused by the deprecation of django.utils.unittest.

Thanks Preston Timmons and Carl Meyer for their advice.

Fixed #20680.