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):
        """Adds a role to a user.

        :param user: The user to manipulate
        :param role: The role to add to the user
        """
        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