We just got bitten by this issue because we are trying to be compatible across 2.x and 3.x (including 3.0-3.2). For anyone who runs into the "missing 1 required keyword-only argument: 'ctx'" here is an import statement that works:

try:
    from multiprocessing import SimpleQueue
except ImportError:
    from multiprocessing.queues import SimpleQueue

Replace SimpleQueue with JoinableQueue if you need that. Importing in the other order will wind you up in problems in 3.4.2+.