使用HttpRequest作为django-celery task时报错

我在用django-celery时尝试把httprequest作为参数调用task,结果保用一下错误，求解哪里粗错了？

    add_scan_record.delay(request, card.id)
  File "/Users/user/qrcardenv/lib/python2.7/site-packages/celery/app/task.py", line 358, in delay
    return self.apply_async(args, kwargs)
  File "/Users/user/qrcardenv/lib/python2.7/site-packages/celery/app/task.py", line 474, in apply_async
    **options)
  File "/Users/user/qrcardenv/lib/python2.7/site-packages/celery/app/amqp.py", line 249, in publish_task
    **kwargs
  File "/Users/user/qrcardenv/lib/python2.7/site-packages/kombu/messaging.py", line 157, in publish
    compression, headers)
  File "/Users/user/qrcardenv/lib/python2.7/site-packages/kombu/messaging.py", line 233, in _prepare
    body) = encode(body, serializer=serializer)
  File "/Users/user/qrcardenv/lib/python2.7/site-packages/kombu/serialization.py", line 170, in encode
    payload = encoder(data)
  File "/Users/user/qrcardenv/lib/python2.7/site-packages/kombu/serialization.py", line 356, in dumps
    return dumper(obj, protocol=pickle_protocol)
PicklingError: Can't pickle <type 'cStringIO.StringO'>: attribute lookup cStringIO.StringO failed