diff -r 268662aac075 -r 2c4f656c8e9f mercurial/utils/interfaceutil.py
--- a/mercurial/utils/interfaceutil.py	Sun Aug 18 00:45:33 2019 +0300
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,40 +0,0 @@
-# interfaceutil.py - Utilities for declaring interfaces.
-#
-# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
-#
-# This software may be used and distributed according to the terms of the
-# GNU General Public License version 2 or any later version.
-
-# zope.interface imposes a run-time cost due to module import overhead and
-# bookkeeping for declaring interfaces. So, we use stubs for various
-# zope.interface primitives unless instructed otherwise.
-
-from __future__ import absolute_import
-
-from .. import (
-    encoding,
-)
-
-if encoding.environ.get('HGREALINTERFACES'):
-    from ..thirdparty.zope import (
-        interface as zi,
-    )
-
-    Attribute = zi.Attribute
-    Interface = zi.Interface
-    implementer = zi.implementer
-else:
-    class Attribute(object):
-        def __init__(self, __name__, __doc__=''):
-            pass
-
-    class Interface(object):
-        def __init__(self, name, bases=(), attrs=None, __doc__=None,
-                 __module__=None):
-            pass
-
-    def implementer(*ifaces):
-        def wrapper(cls):
-            return cls
-
-        return wrapper