'Revoke a task
**Example request**:
.. sourcecode:: http
POST /api/task/revoke/1480b55c-b8b2-462c-985e-24af3e9158f9?terminate=true
Content-Length: 0
Content-Type: application/x-www-form-urlencoded; charset=utf-8
Host: localhost:5555
**Example response**:
.. sourcecode:: http
HTTP/1.1 200 OK
Content-Length: 61
Content-Type: application/json; charset=UTF-8
"message": "Revoked \'1480b55c-b8b2-462c-985e-24af3e9158f9\'"
:query terminate: terminate the task if it is running
:reqheader Authorization: optional OAuth token to authenticate
:statuscode 200: no error
:statuscode 401: unauthorized request'

@web.authenticated
def post(self, taskid):

    logger.info("Revoking    task    '%s'", taskid)
    terminate = self.get_argument('terminate', default=False, type=bool)
    self.capp.control.revoke(taskid, terminate=terminate)
    self.write(dict(message=("Revoked    '%s'" % taskid)))
