diff -r 1fbbb8e83392 -r e3732c3ab92d mercurial/ui.py
--- a/mercurial/ui.py	Sun Mar 04 18:21:16 2018 -0500
+++ b/mercurial/ui.py	Sun Mar 04 18:34:46 2018 -0500
@@ -800,7 +800,8 @@
             user = self.prompt(_("enter a commit username:"), default=None)
         if user is None and not self.interactive():
             try:
-                user = '%s@%s' % (util.getuser(), socket.getfqdn())
+                user = '%s@%s' % (util.getuser(),
+                                  encoding.strtolocal(socket.getfqdn()))
                 self.warn(_("no username found, using '%s' instead\n") % user)
             except KeyError:
                 pass