IMO adding a Popen(errors=...) parameter would be a new feature for 3.6+ only. Also, the patch does not take the error handler into account when encoding and decoding multiple PIPEs in communicate().

I think it would be better to fix this bug in Lib/distutils/_msvccompiler.py only. The equivalent bug fix would look like:

out = subprocess.check_output(
    ...,
    stderr=subprocess.STDOUT,
    # No universal_newlines!
)
...
out = io.TextIOWrapper(io.BytesIO(out), errors="surrogateescape").read()

Or maybe a simpler version is sufficient: (I’m not familiar enough with the use case or Windows to say.)

out = out.decode("ascii", "surrogateescape")