This is related to http://bugs.python.org/issue14151. 
When using an AF_UNIX address with multiprocessing.connection.Listener or Client, the following error will occur, due to the fact that AF_UNIX is not present in socket module.

>>> import multiprocessing.connection as con
>>> con.Listener('/var/a.pipe')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python31\lib\multiprocessing\connection.py", line 97, in __init__
    self._listener = SocketListener(address, family, backlog)
  File "C:\Python31\lib\multiprocessing\connection.py", line 216, in __init__
    self._socket = socket.socket(getattr(socket, family))
AttributeError: 'module' object has no attribute 'AF_UNIX'


The attached patch fixes this issue, the check is done in the newly added _validate_family, where a similar check is done for AF_PIPE on Unix systems.