--- a/mercurial/subrepo.py	Sat Sep 30 07:45:41 2017 -0400
+++ b/mercurial/subrepo.py	Sat Sep 30 07:45:51 2017 -0400
@@ -600,7 +600,6 @@
         walk recursively through the directory tree, finding all files
         matched by the match function
         '''
-        pass
 
     def forget(self, match, prefix):
         return ([], [])