Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 551, in __bootstrap_inner
    self.run()
  File "/usr/share/electrum-server/processor.py", line 246, in run
    self.update()
  File "/usr/share/electrum-server/processor.py", line 260, in update
    self.send_response(internal_id, response)
  File "/usr/share/electrum-server/processor.py", line 276, in send_response
    session.send_response(response)
  File "/usr/share/electrum-server/transports/stratum_tcp.py", line 30, in send_response
    data = json.dumps(response) + "\n"
  File "/usr/lib/python2.7/json/__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
  File "/usr/lib/python2.7/json/encoder.py", line 201, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python2.7/json/encoder.py", line 264, in iterencode
    return _iterencode(o, 0)
  File "/usr/lib/python2.7/json/encoder.py", line 178, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: is not JSON serializable