diff -r b39958d6b81b -r aac4be30e250 mercurial/cmdutil.py
--- a/mercurial/cmdutil.py	Thu May 03 18:39:58 2018 +0900
+++ b/mercurial/cmdutil.py	Sat May 26 12:14:04 2018 +0900
@@ -10,7 +10,6 @@
 import errno
 import os
 import re
-import tempfile
 
 from .i18n import _
 from .node import (
@@ -329,7 +328,7 @@
         try:
             # backup continues
             for f in tobackup:
-                fd, tmpname = tempfile.mkstemp(prefix=f.replace('/', '_')+'.',
+                fd, tmpname = pycompat.mkstemp(prefix=f.replace('/', '_') + '.',
                                                dir=backupdir)
                 os.close(fd)
                 ui.debug('backup %r as %r\n' % (f, tmpname))