--- a/mercurial/scmposix.py	Thu Oct 20 21:38:44 2016 +0900
+++ b/mercurial/scmposix.py	Thu Oct 20 21:42:11 2016 +0900
@@ -41,11 +41,11 @@
     else:
         return [os.path.expanduser('~/.hgrc')]
 
-def termwidth():
+def termwidth(ui):
     try:
         import array
         import termios
-        for dev in (sys.stderr, sys.stdout, sys.stdin):
+        for dev in (ui.ferr, ui.fout, ui.fin):
             try:
                 try:
                     fd = dev.fileno()