Adds the 'd_p_list' permission to a user object when provided
            a user_email and portal_id.

def add_dplist_permission_for_user_on_portal(self, user_email, portal_id):
        """ Adds the 'd_p_list' permission to a user object when provided
            a user_email and portal_id."""
        _id = self.get_user_id_from_email(user_email)
        print(self.get_user_permission_from_email(user_email))
        retval = self.add_user_permission(  _id, json.dumps( 
                        [{'access': 'd_p_list', 'oid':{'id': portal_id, 'type':'Portal'}}] 
                )
        )
        print(self.get_user_permission_from_email(user_email))
        return retval