[patch] date_hierarchy in model is not checked for validity.

[Simon Greenhill, dev@…]

When one of the models has the date_hierarchy incorrectly set ( i.e. typo, or the string isn't a field in the model ), the admin section fails with a template syntax error:

FieldDoesNotExist at /admin/<app>/<something>/
Link has no field named '<misspelt field name>')

I've modified django.core.management.get_validation_errors to check that the field specified in date_hierarchy is a valid model field.

[dev@…]

This might also fix ticket:1377 - Looking at it, it looks like that error occured due to date_hierarchy being passed a tuple and not a string.

[Adrian Holovaty]

(In [3516]) Fixed #2467 -- Improved model validator to check date_hierarchy. Thanks, Simon Greenhill