--- a/mercurial/pycompat.py	Thu May 03 18:39:58 2018 +0900
+++ b/mercurial/pycompat.py	Sat May 26 12:14:04 2018 +0900
@@ -15,6 +15,7 @@
 import os
 import shlex
 import sys
+import tempfile
 
 ispy3 = (sys.version_info[0] >= 3)
 ispypy = (r'__pypy__' in sys.builtin_module_names)
@@ -384,3 +385,7 @@
 
 def gnugetoptb(args, shortlist, namelist):
     return _getoptbwrapper(getopt.gnu_getopt, args, shortlist, namelist)
+
+# text=True is not supported; use util.from/tonativeeol() instead
+def mkstemp(suffix=b'', prefix=b'tmp', dir=None):
+    return tempfile.mkstemp(suffix, prefix, dir)