diff -r 48dea083f66d -r 82f1ef8b4477 mercurial/ui.py
--- a/mercurial/ui.py	Mon Feb 13 20:06:38 2017 +0530
+++ b/mercurial/ui.py	Mon Feb 13 22:15:28 2017 +0530
@@ -1038,7 +1038,7 @@
                                       suffix=extra['suffix'], text=True,
                                       dir=rdir)
         try:
-            f = os.fdopen(fd, "w")
+            f = os.fdopen(fd, pycompat.sysstr("w"))
             f.write(text)
             f.close()