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The problem with the thread issue is that -- as I drew
attention to when the module was considered for addition to
stdlib -- there is thread synchronization in there, but it
is untested, and I now strongly suspect is broken.  I'm not
thread-competent enough to be confident in my testing of any
fix I might attempt.

I now regret not simply stripping all the thread
synchronization out from the start.  Perhaps that should be
done now, and a comment like that you suggest added?  Advice
here is most welcome!

Re the rest: As per my last comment, will resubmit API
changes (ie. method additions) as separate patch for 2.5. 
I'll split the rest up into separate patches, too. 
Therefore, I'm unassigning Jeremy and will close this patch
when I've opened the new ones.