util.termwidth: check stderr first as it's least likely to be redirected

mercurial/util.py

@@ -1253,7 +1253,7 b' def termwidth():'
             pass
     try:
         import termios, array, fcntl
-        for dev in (sys.stdout, sys.stdin):
+        for dev in (sys.stderr, sys.stdout, sys.stdin):
             try:
                 try:
                     fd = dev.fileno()