def __register_user(self, google_user, permission=UserPermission.normal):
"""
Register the user.
:param google_user: The google.appengine.api.users.get_current_user().
:param permission: The user's permission.
:return: The datastore.user_model.UserModel object.
"""
user = User()
user.email = google_user.email().lower()
user.name = google_user.nickname()
user.permission = permission
user.put()
user.get(user.key())
return user
