Datetime serialization issue on reservation notification email celery task

[jwalgran]

I noticed this regression while testing updates to reservation PDF generation.

 Task apps.mail.tasks.notify_reservation_confirmed[b2cd993c-421d-4a9f-8b6b-d1ce951f52ba] raised unexpected: EncodeError(TypeError('datetime.datetime(2015, 4, 13, 15, 39, 31, 390209, tzinfo=<UTC>) is not JSON serializable',),)
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/celery/app/trace.py", line 283, in trace_task
    uuid, retval, SUCCESS, request=task_request,
  File "/usr/local/lib/python2.7/dist-packages/celery/backends/base.py", line 256, in store_result
    request=request, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/celery/backends/base.py", line 486, in _store_result
    self.set(self.get_key_for_task(task_id), self.encode(meta))
  File "/usr/local/lib/python2.7/dist-packages/celery/backends/base.py", line 182, in encode
    _, _, payload = dumps(data, serializer=self.serializer)
  File "/usr/local/lib/python2.7/dist-packages/kombu/serialization.py", line 164, in dumps
    payload = encoder(data)
  File "/usr/lib/python2.7/contextlib.py", line 35, in __exit__
    self.gen.throw(type, value, traceback)
  File "/usr/local/lib/python2.7/dist-packages/kombu/serialization.py", line 59, in _reraise_errors
    reraise(wrapper, wrapper(exc), sys.exc_info()[2])
  File "/usr/local/lib/python2.7/dist-packages/kombu/serialization.py", line 55, in _reraise_errors
    yield
  File "/usr/local/lib/python2.7/dist-packages/kombu/serialization.py", line 164, in dumps
    payload = encoder(data)
  File "/usr/local/lib/python2.7/dist-packages/anyjson/__init__.py", line 141, in dumps
    return implementation.dumps(value)
  File "/usr/local/lib/python2.7/dist-packages/anyjson/__init__.py", line 87, in dumps
    return self._encode(data)
  File "/usr/lib/python2.7/dist-packages/simplejson/__init__.py", line 354, in dumps
    return _default_encoder.encode(obj)
  File "/usr/lib/python2.7/dist-packages/simplejson/encoder.py", line 262, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python2.7/dist-packages/simplejson/encoder.py", line 340, in iterencode
    return _iterencode(o, 0)
  File "/usr/lib/python2.7/dist-packages/simplejson/encoder.py", line 239, in default
    raise TypeError(repr(o) + " is not JSON serializable")
EncodeError: datetime.datetime(2015, 4, 13, 15, 39, 31, 390209, tzinfo=<UTC>) is not JSON serializable

[maurizi]

We may be able to fix this by switching to a different Celery serialization format, like pickle

[kdeloach]

Looks like this error occurs after successfully sending emails, which would explain why sending email works on staging.