https://bugs.winehq.org/show_bug.cgi?id=42474
--- Comment #16 from Sebastian Ernst ernst@pleiszenburg.de --- Relaying this from Eryk Sun in the Python bug tracker: "PathCchCombineEx isn't an import dependency. It's used dynamically via LoadLibraryW and GetProcAddress, with a fallback to PathCombineW. Does Wine maybe have a stub for this function that returns E_NOTIMPL (not implemented)?"
I looked at the code to understand what he says: https://github.com/python/cpython/blob/3.6/PC/getpathp.c#L219 Lines 219 to 242 is really where all the relevant stuff happens. Python tries to get the address of PathCchCombineEx. If that fails, it falls back to PathCombineW.
My understanding is that Wine even if it is set to Windows Vista or 7 returns an address for PathCchCombineEx which does not allow Python to fall back to PathCombineW. If PathCchCombineEx just was not there (in Windows Vista and 7 settings) or would return E_NOTIMPL, it might allow Python 3.6 to work (assuming a working implementation of PathCombineW).
Btw, Python 3.5 was using its own logic at this point: https://github.com/python/cpython/blob/3.5/PC/getpathp.c#L167
Does this information allow you to fix this issue?