diff -r d8d4fa9a7f18 -r a0ec05d93c8e mercurial/dispatch.py
--- a/mercurial/dispatch.py	Thu Jan 16 13:34:04 2020 +0100
+++ b/mercurial/dispatch.py	Mon Feb 10 17:31:05 2020 -0500
@@ -624,7 +624,7 @@
         except error.AmbiguousCommand:
             self.badalias = _(
                 b"alias '%s' resolves to ambiguous command '%s'"
-            ) % (self.name, cmd)
+            ) % (self.name, cmd,)
 
     def _populatehelp(self, ui, name, cmd, fn, defaulthelp=None):
         # confine strings to be passed to i18n.gettext()