Add "G:\русский язык" to a pth file and start python. it fails with 

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Failed to import the site module
Traceback (most recent call last):
  File "C:\Program Files\ROXAR\RMS dev_release\windows-amd64-vc_14_0-release\bin\lib\site.py", line 546, in <module>
    main()
  File "C:\Program Files\ROXAR\RMS dev_release\windows-amd64-vc_14_0-release\bin\lib\site.py", line 532, in main
    known_paths = addusersitepackages(known_paths)
  File "C:\Program Files\ROXAR\RMS dev_release\windows-amd64-vc_14_0-release\bin\lib\site.py", line 287, in addusersitepackages
    addsitedir(user_site, known_paths)
  File "C:\Program Files\ROXAR\RMS dev_release\windows-amd64-vc_14_0-release\bin\lib\site.py", line 209, in addsitedir
    addpackage(sitedir, name, known_paths)
  File "C:\Program Files\ROXAR\RMS dev_release\windows-amd64-vc_14_0-release\bin\lib\site.py", line 165, in addpackage
    for n, line in enumerate(f):
  File "C:\Program Files\ROXAR\RMS dev_release\windows-amd64-vc_14_0-release\bin\lib\encodings\cp1252.py", line 23, in decode
    return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 8: character maps to <undefined>
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This might very well have sideeffects, but adding "encoding='utf-8'" to the open() call in site.py def addpackage seems to fix the issue for me