A few problems have been found when working with model creation.
When using multiple databases, we'd sometimes try to create models in

the database using the default database. This happened because we

weren't passing along the explicit database we're working with, which

is now a requirement for the function.
There was also an issue on Django 1.6 with working with models across

more than one app sharing the same legacy app label. When fetching

models for an app using Django's get_models(), it wouldn't actually

check that the models being returned are for the provided app, meaning

that we'd get the same models back more than once, hitting conflicts

when creating them. We now check this ourselves, making sure each

model's module resides somewhere within the app.
We also hit one other subtle issue where we were generating a list of

new models incorrectly. This was only used for the signals, but broke

some signal handlers out there. We now correctly turn this into a

flat list of new models.

Unit tests pass on Django 1.6 and 1.11.
Tested against Review Board, which had the app conflict issue.