Just did this.  Required jumping through some hoops:
* json_serializer was imported across modules... but itself imported from django.  Just import directly from django in each place, methinks.
* Splitting of model_sync.py from models.py created a dependency loop.  Best way I've seen to resolve these is to do imports within functions.  I know it breaks a convention, but I think it's a smaller convention to break than to put these non-model functions into models.py.

If it's not the favored design, glad to discuss!  I implemented knowing that I may wind up reverting back to the previous version (everything in one file).

Anyway, did some basic sync tests to work things out; seems to be working now.