``RegistrationView`` only supports ``ModelForm`` but not conventional forms about django-registration

[ubernostrum]

This is a much larger and more complex feature request than I think you're aware of, because what you're really heading down the path of doing is "what if I have a bunch of account-related model instances to create in a complex possibly-multi-step form wizard". Which would require some major code changes in django-registration to try to support. For now, it operates on the assumption that signing up a user involves one form, tied to one model, and that any additional forms or things you want to process or create afterward will be done in your own code.