The code I've just committed to issue10197 means that the get[status]output functions now pass their (few) tests on all platforms. More by chance than judgement, that change employed universal_newlines which has the effect of forcing the output of check_output to string rather than bytes.

Having just re-read all the comments, we have three positions:

a) Do nothing: these are outdated functions and anyone who has a problem with undecodable bytes will have to use one of the other functions where they have more control.

b) Use the surrogateescape encoding in every case to produce *some* kind of output rather than an exception.

c) Tweak the code to produce bytes in every case. This is actually simple: removing universal_newlines support will do this. (I already have working code for this).

I think (b) is more trouble than it's worth. So (a) Do Nothing; or (c) Produce Bytes.

Going by the law of "Status Quo wins", if no-one chimes in with a strong case for switching to bytes in a few days, I propose to close this as Won't Fix.