Davin Potts added the comment:

The example demonstrating the issue is reproducible on Windows (tested on 
Windows 7 64-bit, specifically) with 2.7.9.  Complications arising from how 
multiprocessing creates new processes on Windows combined with conventions in 
the import system in 2.7.9 result in the problem being triggered here.

This issue is specific to Windows platform use:  It was not possible to 
reproduce the issue on OS X nor Linux with 2.7.9.

As played out in the discussion around issue10845 (long since closed), 
solutions were devised and put into place as part of PEP451, exposed first in 
Python 3.4.  And so it was not possible to reproduce this issue with default 
(3.5) on Windows 7.

It is very much appreciated anytime such a nice, clean demonstration code is 
provided and more than doubly so anytime a proposed patch is also offered.  
While the supplied/proposed patch does provide some workaround it is not yet a 
comprehensive solution and appears to potentially cause complications in other 
scenarios.  The current best effort at a comprehensive solution is reflected in 
the changes designed and now implemented in 3.4.

Two aspects to the resolution on this issue:
* For the 2.x branches, it is unlikely that we will see a backport of PEP451 
and so a more comprehensive solution might depend upon some other fundamental 
changes to how multiprocessing operates on Windows platforms but there are no 
such plans to invest that level of effort into 2.7.  It is still possible that 
someone might become so motivated about multiprocessing+Windows+2.7 but that 
seems ever more unlikely.
* For the 3.x branches, we have verified that changes in 3.4 have resulted in a 
fix for this particular issue.  Overall, marking this as fixed in 3.[4-5].

----------
nosy: +davin
resolution:  -> fixed
stage: needs patch -> resolved
status: open -> closed

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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue8534>
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