Perform an always failing task.

def always_fail(cls, request) -> [
            (200, 'Ok', String),
            (406, 'Not Acceptable', Void)]:
        '''Perform an always failing task.'''
        task_id = uuid4().hex.upper()[:5]
        log.info('Starting always FAILING task {}'.format(task_id))
        for i in range(randint(0, MAX_LOOP_DURATION)):
            yield
        Respond(406)
        Respond(200, 'Foobar')