On cygwin, py3k aborts if lanches it via symbolic link.

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Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
Fatal Python error: Py_Initialize: can't initialize sys standard streams
ImportError: No module named encodings.utf_8
Aborted (core dumped)

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This is because mbstowcs() on cygwin is broken, so _Py_wreadlink() in
Modules/getpath.c is also broken. I'll attach two patches to fix this. I
don't know which is better.