[Answer]-Django-registration with is_super_user on by default.

You’re looking for signals. Add signals.py to your app and then

# handle signal
def user_registered(sender, user, request, **kwarg):
   user.is_superuser = True
   user.save()

# register signal
user_registered.connect(user_registered)

See explanation at https://django-registration.readthedocs.org/en/latest/signals.html