I think this is worth unifying, but I'm concerned about making expanduser() return the original path on Windows - "~name" is a valid filename/relative path, and so code that does mkdir(expanduser("~nonuser/dir")) could create garbage in the current directory. I'd rather just raise OSError (or I guess RuntimeError, for consistency).

Long term, I'd like to see it switch to calling GetProfilesDirectory on Windows, but that's separate from this change, and doesn't invalidate this one.

Reading through the discussion, it seems like the primary concern about the change is "change for change sake". I think the amount and kind of code that's being removed is a good thing, and it's better represented as an "expand" step in the accessor than a "get" from the path.

So let's get it merged, probably(?) with a stronger error for the unknown users, but happy to be talked out of that. And only for 3.10.