Thanks chrj for the suggestion.

Thanks Stephen Burrows for work on the patch as well.

Forwardport of 2914f669 from stable/1.7.x

Thanks Aymeric Augustin for the report.

Thanks Anssi Kääriäinen for the idea and Simon Charette for the
review.

Thanks Piotr Kasprzyk for help with the patch.

This is the result of Christopher Medrela's 2013 Summer of Code project.

Thanks also to Preston Holmes, Tim Graham, Anssi Kääriäinen, Florian
Apolloner, and Alex Gaynor for review notes along the way.

Also: Fixes #8579, fixes #3055, fixes #19844.

Signed-off-by: Jason Myers <jason@jasonamyers.com>

Thanks Tuttle for the report.

Thanks rm_ for the suggestion.

Thanks stanislas.guerra at gmail.com for the report.

Thanks to Collin Anderson for the suggestion and Tim Graham for
reviewing the patch.

Refs #18681.

This also starts the deprecation of ModelAdmin.declared_fieldsets

Should be unneeded with Python 2.7 and up.
Added some unicode_literals along the way.

Refs #20680.

Fixed #18681 -- BaseModelAdmin.get_form and InlineModelAdmin.get_formset no longer bypass get_fieldsets

Thanks msopacua for the report.

Moved admin validation code to classes and have those be class
attributes to the ModelAdmin classes.

This also updates all dependent functionality, including modelform_factory
 and modelformset_factory, and the generic views `ModelFormMixin`,
 `CreateView` and `UpdateView` which gain a new `fields` attribute.