'Determinate if async request was successful.
An async_request retrieves for a task object that can be successfully
retrieved (self.status == OK), but the asynchronous task (the body of
the HTTP response) which we are asking for has finished with an error.
So this method checks if the status code is \'OK\' and if the task
has finished successfully.
:rtype:  ``bool``
:return: successful asynchronous request or not'

def async_success(self):

    if self.success():
        task = self.parse_body()
        return (task.findtext('state') == 'FINISHED_SUCCESSFULLY')
    else:
        return False
