Try to add this lines to the top of your settings file:
import djangodjango.setup()
And if this will not help you try to remove third-party applications from your installed apps list one-by-one.
I'd a custom function written on one of my models __init__.py file. It was causing the error. When I moved this function from __init__.py it worked.
__init__.py
My problem was that I tried to import a Django model before calling django.setup()
django.setup()
This worked for me:
import djangodjango.setup()from myapp.models import MyModel
The above script is in the project root folder.