[Django]-Switch to Django Custom User Model, Groups and Permissions

You have not created appropriate table in the database.
Make tables before switching user model:

python manage.py syncdb
#or if you're use south
python manage.py schemamigration core --initial
python manage.py migrate core

Then write custom migration script for you user data, or you’ll lose it.

Look this manual and this documentation, it’ll help you to understend what should be done.