I am trying to use the email field in the default Django user model as the username. I am using Django 1.5 and I saw that the default user has a USERNAME_FIELD
You have to write a new Custom User Class by extending the AbstractBaseUser and not AbstractUser
Declare your email as the USERNAME_FIELD there
Optionally you can also declare a custom user manager that extends from BaseUserManager to handle the username required constraint. You can remove username from that manager's create_user function
#Your app's __init__.py
from django.contrib.auth.models import User
User.USERNAME_FIELD = 'email'