Fixed TypeError when rendering ModelState with multiple bases.
Removed unreachable `else` in `try` block.
Renamed syncdb to migrate in spatialite backend
Fixed #19678 -- GeoDjango test failure with spatialite >= 3.0.

Thanks Julien for the report and Claude for the fix.
Merge pull request #2037 from bmispelon/invalidbaseserror

Fixed TypeError when rendering ModelState with multiple bases.
Added app_label to the error message when field reconstructing fails.
Fixed error in ManyToManyField.deconstruct().
Fixed ModelState breaking when unique_together has unhashable elements.
Made the migration detector use meta.local_fields instead of meta.fields.

Refs #21010.

Thanks to Loïc for the patch.
Added missing deconstruct() methods.
Added new 'srtext' spatialite 4.x SpatialRefSys column to its model.

This is for general consistency in the GeoDjango DB backends.
Thanks Claude for the fix.

Refs #19678.
Removed a u'' prefix that prevented the docs from building on Python 3.2.
Fixed #21554 -- Incorrect SQL generated when using multiple inheritance.
Fixed #21566 -- Fixed AttributeError when using bulk_create with ForeignObject.
Corrected a flake8 issue -- this line is imported for the purpose of re-exposing the name