The culprit character is hidden between "Issue #" and "20540" at line 400 of C:\Python35\Lib\multiprocessing\connection.py. https://bugs.python.org/issue20540 and https://hg.python.org/cpython/rev/125c24f47f3c refers. I'm asking as I've just spent 30 minutes tracking down why my debug code would bomb when running on 3.5, but not 2.7 or 3.2 through 3.4. -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence