--- a/mercurial/vfs.py	Sun Jul 02 04:51:03 2017 +0200
+++ b/mercurial/vfs.py	Wed Dec 26 13:44:23 2018 +0100
@@ -46,6 +46,9 @@
         '''Prevent instantiation; don't call this from subclasses.'''
         raise NotImplementedError('attempted instantiating ' + str(type(self)))
 
+    def _auditpath(self, path, mode):
+        pass
+
     def tryread(self, path):
         '''gracefully return an empty string for missing files'''
         try: