Update router.py
Update router.py

Sometimes we create migrations for local development databases but someone adds an invalid import, in this situation the real error is hidden from the developer as only `Can't import models module: True` is returned instead of the real issue: `No module named 'peewee_extra_fields'`. This PR is meant to help prevent others from having to download this library and place it in the editable mode with a debugger in it.. just to find out the library works as expected.
klen/peewee_migrate