On Debian Hurd, there is no sem_open implementation. When I try there to create a Queue, I get different errors, depending on the Python version:

import multiprocessing
q = multiprocessing.Queue()

gives on Python 2.7.9:

maxsize = 0

    def Queue(maxsize=0):
        '''
        Returns a queue object
        '''
>       from multiprocessing.queues import Queue

/usr/lib/python2.7/multiprocessing/__init__.py:217: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

    __all__ = ['Queue', 'SimpleQueue', 'JoinableQueue']
    
    import sys
    import os
    import threading
    import collections
    import time
    import atexit
    import weakref
    
    from Queue import Empty, Full
    import _multiprocessing
    from multiprocessing import Pipe
>   from multiprocessing.synchronize import Lock, BoundedSemaphore, Semaphore, Condition

/usr/lib/python2.7/multiprocessing/queues.py:48: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

    'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Condition', 'Event'
    ]
    
    import threading
    import os
    import sys
    
    from time import time as _time, sleep as _sleep
    
    import _multiprocessing
    from multiprocessing.process import current_process
    from multiprocessing.util import Finalize, register_after_fork, debug
    from multiprocessing.forking import assert_spawning, Popen
    
    # Try to import the mp.synchronize module cleanly, if it fails
    # raise ImportError for platforms lacking a working sem_open implementation.
    # See issue 3770
    try:
    from _multiprocessing import SemLock
    except (ImportError):
    raise ImportError("This platform lacks a functioning sem_open" +
                      " implementation, therefore, the required" +
                      " synchronization primitives needed will not" +
>                     " function, see issue 3770.")
E                     ImportError: This platform lacks a functioning sem_open implementation, therefore, the required synchronization primitives needed will not function, see issue 3770.

/usr/lib/python2.7/multiprocessing/synchronize.py:59: ImportError

and on 3.4.2:

self = <multiprocessing.context.DefaultContext object at 0x1449b0c>, maxsize = 0

    def Queue(self, maxsize=0):
        '''Returns a queue object'''
        from .queues import Queue
>       return Queue(maxsize, ctx=self.get_context())

/usr/lib/python3.4/multiprocessing/context.py:101: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <multiprocessing.queues.Queue object at 0x511e8cc>, maxsize = 0

    def __init__(self, maxsize=0, *, ctx):
        if maxsize <= 0:
>           maxsize = _multiprocessing.SemLock.SEM_VALUE_MAX
E           AttributeError: 'module' object has no attribute 'SemLock'

/usr/lib/python3.4/multiprocessing/queues.py:38: AttributeError

Both traces are actually copied from Debian build logs:
2.7.9: https://buildd.debian.org/status/fetch.php?pkg=python-astropy&arch=hurd-i386&ver=1.0~rc1-1&stamp=1422724845
3.4.2: https://buildd.debian.org/status/fetch.php?pkg=python-astropy&arch=hurd-i386&ver=1.0~rc1-2&stamp=1423153281

Neither for 2.7.9 nor for 3.4.2 this behaviour is documented. Also, I would expect to have a NotImplementedError and not an ImportError or an AttributeError in such a case.

Please:

* document the behaviour of multiprocessing.Queue() in the case of an absent sem_open for both Python2 and Python3

* Consider raising NotImplementedError or being consistent in some other way.