I am struggling with the same issue as Anthony. To provide a more direct response to Manjusaka's query:

python -c "import os; print(os.environ.get(\"PATHEXT\", \"\").split(os.pathsep))"
['.COM', '.EXE', '.BAT', '.CMD', '.VBS', '.VBE', '.JS', '.JSE', '.WSF', '.WSH', '.MSC']

Like Anthony, wondering if this should be it's own issue. Simply supporting paths with separators shouldn't, I think, lead to any of the ambiguities of matching a file exactly, without PATHEXT treatment.