diff -r 91d63fd58e7d -r f1d6021453c2 mercurial/scmutil.py
--- a/mercurial/scmutil.py	Tue Sep 25 22:11:17 2018 -0400
+++ b/mercurial/scmutil.py	Tue Sep 25 23:25:36 2018 -0400
@@ -1339,7 +1339,7 @@
         if spec.startswith("shell:"):
             # external commands should be run relative to the repo root
             cmd = spec[6:]
-            proc = subprocess.Popen(pycompat.rapply(procutil.tonativestr, cmd),
+            proc = subprocess.Popen(procutil.tonativestr(cmd),
                                     shell=True, bufsize=-1,
                                     close_fds=procutil.closefds,
                                     stdout=subprocess.PIPE,