Restore model_class for creating user as this code is shared with Toolshed

        Create a new user.

        """

        self._error_on_duplicate_email(email)

        user = User(email=email)

        user = self.model_class(email=email)

        if password:

            user.set_password_cleartext(password)

        else:

        session.add(user)

        try:

            # Creating a private role will commit the session

            user.attempt_create_private_role()

            self.app.security_agent.create_user_role(user, self.app)

        except exc.IntegrityError as db_err:

            raise exceptions.Conflict(str(db_err))

        return user