@IgorNovozhilov how about adding a try..except.
If the above (and below) code doesn't work, then try opening with the encoding.
I prefer that approach as that will leave it backward compatible (ensuring we don't introduce any other issues).
If you can make that change I can accept this and create a build soon.

here's what I'm suggesting:

try:
    with open(path) as f:
        source = f.read()
except UnicodeDecodeError:
    with open(path, encoding=encoding) as f:
        source = f.read()

Thanks

ready