https://bugs.winehq.org/show_bug.cgi?id=42474
--- Comment #18 from Sebastian Ernst ernst@pleiszenburg.de --- I just did.
In the meantime, there are two lines of code which could trigger this exact fatal error (the messages are ironically identical): https://github.com/python/cpython/blob/3.6/PC/getpathp.c#L237 https://github.com/python/cpython/blob/3.6/PC/getpathp.c#L240
If it is the latter, you might be looking at a bug in your implementation of PathCombineW (?). I do not have a tool chain up and running for re-compiling Python for Windows with a bit more verbosity at this very spot ... Maybe this would help.