'Adds a role to a user.
:param user: The user to manipulate
:param role: The role to add to the user'

def add_role_to_user(self, user, role):

    (user, role) = self._prepare_role_modify_args(user, role)
    if (role not in user.roles):
        user.roles.append(role)
        self.put(user)
        return True
    return False
