* bpo-32731: Raise OSError from any failure in getpass.getuser()
Previously, if the username was not set in certain environment variables, ImportError escaped on Windows systems, and it was possible for KeyError to escape on other systems if getpwuid() failed.
If the input stream encoding couldn't encode one or more of the
non-ascii characters in the prompt, it would fail, throwing a
UnicodeEncodeError. Now if that happens we re-encoding using the
'replace' error handler.
Patch by Kushal Das.
Also fixes a resource warning that occurred when the fallback is taken.
Patch by Serhiy Storchaka.
(We couldn't figure out how to write tests for this.)
