This error happens a lot in the same buildbot in different tests:

raceback (most recent call last):
  File "/usr/home/buildbot/python/3.7.koobs-freebsd-current/build/Lib/multiprocessing/process.py", line 297, in _bootstrap
    self.run()
  File "/usr/home/buildbot/python/3.7.koobs-freebsd-current/build/Lib/multiprocessing/process.py", line 99, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/home/buildbot/python/3.7.koobs-freebsd-current/build/Lib/test/_test_multiprocessing.py", line 3335, in child_access
    w = conn.recv()
  File "/usr/home/buildbot/python/3.7.koobs-freebsd-current/build/Lib/multiprocessing/connection.py", line 251, in recv
    return _ForkingPickler.loads(buf.getbuffer())
  File "/usr/home/buildbot/python/3.7.koobs-freebsd-current/build/Lib/multiprocessing/connection.py", line 960, in rebuild_connection
    fd = df.detach()
  File "/usr/home/buildbot/python/3.7.koobs-freebsd-current/build/Lib/multiprocessing/resource_sharer.py", line 58, in detach
    return reduction.recv_handle(conn)
  File "/usr/home/buildbot/python/3.7.koobs-freebsd-current/build/Lib/multiprocessing/reduction.py", line 185, in recv_handle
    return recvfds(s, 1)[0]
  File "/usr/home/buildbot/python/3.7.koobs-freebsd-current/build/Lib/multiprocessing/reduction.py", line 161, in recvfds
    len(ancdata))
RuntimeError: received 0 items of ancdata