title: Pickle is refusing to serialize content with celery reporting ContentDisallowed: Refusing to deserialize untrusted content of type pickle
body: <p>I am trying to put some python object mostly json serializable except datetime.datetime in rabbitmq queue and so using pickle to serialize.</p>
  
  <p>celery_config file:</p>
  
  <pre><code>CELERY_TASK_SERIALIZER = 'pickle'
  CELERY_RESULT_SERIALIZER = 'pickle'
  </code></pre>
  
  <p>It is throwing an exception saying:</p>
  
  <pre><code> File "/usr/local/lib/python2.7/dist-packages/kombu/serialization.py", line 174, in loads
      raise self._for_untrusted_content(content_type, 'untrusted')
  ContentDisallowed: Refusing to deserialize untrusted content of type pickle (application/x-python-serialize)
  </code></pre>
  
  <p><a href="http://docs.celeryproject.org/en/latest/userguide/security.html#serializers" rel="noreferrer">This link</a>
  suggests I do message signing about which I have no clue.</p>
  
  <p>Can someone please guide me through how do I work it out?</p>