embray
commented
5 years ago Although something like this felt vaguely familiar, I had to re-convince myself it's actually as bad as it looks: If an application run by powershell writes something to stderr it detects this and wraps that output in and raises a NativeCommandError, thus technically returning an error.
In other words, it assumes nobody will abuse stderr to write messages that are not actually error messages representing an unrecoverable error condition; it has no concept of how unix programs often use stderr to write any kinds of out-of-band messages, besides strictly errors. Who's right? I don't know. But this has to be worked around. I definitely recall dealing with this at some previous time.
See AppVeyor log.
CC @embray