models: applied bramwelt's 0001-Bug-Fix-for-GanetiError-MultipleObjectsReturned.patch

refs #11445
Test adding duplicate error.

refs #11445
Merge branch 'bug/11445' into develop
Fix GWM at Django 1.4

Django 1.5 added more strict requirements for STATIC_URL. Since our
settings doesn't currently end in a slash, the project fails to test or
run.

Refs #12801