'Revoke access token.
For more information, please refer to the official API reference:
http://developer.openstack.org/api-ref/identity/v3-ext/#revoke-access-token'

def revoke_access_token(self, user_id, access_token_id):

    (resp, body) = self.delete(('users/%s/OS-OAUTH1/access_tokens/%s' % (user_id, access_token_id)))
    self.expected_success(204, resp.status)
    return rest_client.ResponseBody(resp, body)
