AUTH_USER_MODEL refers to model 'accounts.User' that has not been installed

I suspect the problem is one of dependencies. You are importing UserCreationForm at the top of your accounts.models file, where it in turn tries to get the user model - but the rest of that models file has not yet been processed, so User is not defined.

You can easily solve this by following recommended practice and moving the form import and definition into a separate forms.py file.