'Update a user password
For a full list of available parameters, please refer to the official
API reference:
http://developer.openstack.org/api-ref/identity/v3/index.html#change-password-for-user'

def update_user_password(self, user_id, **kwargs):

    update_user = json.dumps({'user': kwargs})
    (resp, _) = self.post(('users/%s/password' % user_id), update_user)
    self.expected_success(204, resp.status)
    return rest_client.ResponseBody(resp)
