diff -r 922b3fae9c7d -r 0dfb5672f015 mercurial/localrepo.py
--- a/mercurial/localrepo.py	Wed Mar 21 18:32:47 2018 -0700
+++ b/mercurial/localrepo.py	Wed Mar 21 19:48:36 2018 -0700
@@ -20,6 +20,9 @@
     nullid,
     short,
 )
+from .thirdparty.zope import (
+    interface as zi,
+)
 from . import (
     bookmarks,
     branchmap,
@@ -318,6 +321,7 @@
 # set to reflect that the extension knows how to handle that requirements.
 featuresetupfuncs = set()
 
+@zi.implementer(repository.completelocalrepository)
 class localrepository(object):
 
     # obsolete experimental requirements: