Python driver fails with unexpected bytes

[ssut]

I'm running tasks using celery in Python with python rethinkdb driver. I followed Ten-minute guide with Rethinkdb and Python and it seems to be running fine for a while, but it fails with UnicodeDecodeError after some time.

[2017-06-18 16:24:00,102: WARNING/PoolWorker-6] b'{"deleted":0,"errors":0,"generated_keys":["cef00e30-fdb1-443e-8313-54ab6da8812d"],"inserted":1,"replaced":0,"skipped":0,"unchanged":0}]}\x02\x00\x00\x00\x00\x00\x00\x00\x94\x00\x00\x00'
[2017-06-18 16:24:00,105: ERROR/PoolWorker-6] Task tasks.crawl[ddaffbc4-e56d-4da8-8304-c5abd243be79] raised unexpected: UnicodeDecodeError('utf-8', b'{"deleted":0,"errors":0,"generated_keys":["cef00e30-fdb1-443e-8313-54ab6da8812d"],"inserted":1,"replaced":0,"skipped":0,"unchanged":0}]}\x02\x00\x00\x00\x00\x00\x00\x00\x94\x00\x00\x00', 144, 145, 'invalid start byte')
Traceback (most recent call last):
  File "/home/ssut/.local/share/virtualenvs/server-NO78Iaa1/lib/python3.6/site-packages/celery/app/trace.py", line 367, in trace_task
  R = retval = fun(*args, **kwargs)
  File "/home/ssut/.local/share/virtualenvs/server-NO78Iaa1/lib/python3.6/site-packages/celery/app/trace.py", line 622, in __protected_call__
  return self.run(*args, **kwargs)
  File "/home/ssut/dev/.../tasks.py", line 215, in crawl
  r.table('logs').insert(log).run(conn)
  File "/home/ssut/.local/share/virtualenvs/server-NO78Iaa1/lib/python3.6/site-packages/rethinkdb/ast.py", line 123, in run
  return c._start(self, **global_optargs)
  File "/home/ssut/.local/share/virtualenvs/server-NO78Iaa1/lib/python3.6/site-packages/rethinkdb/net.py", line 626, in _start
  return self._instance.run_query(q, global_optargs.get('noreply', False))
  File "/home/ssut/.local/share/virtualenvs/server-NO78Iaa1/lib/python3.6/site-packages/rethinkdb/net.py", line 459, in run_query
  res = self._read_response(query)
  File "/home/ssut/.local/share/virtualenvs/server-NO78Iaa1/lib/python3.6/site-packages/rethinkdb/net.py", line 507, in _read_response
  self._parent._get_json_decoder(query))
  File "/home/ssut/.local/share/virtualenvs/server-NO78Iaa1/lib/python3.6/site-packages/rethinkdb/net.py", line 74, in __init__
  json_str = json_str.decode('utf-8')
  UnicodeDecodeError: 'utf-8' codec can't decode byte 0x94 in position 144: invalid start byte

The first line is a hint I modified to check where the error comes from:

I think the root cause of this issue is that the part of the socket receives response from the rethinkdb server does the wrong behavior.