diff -r aea246bc04bd -r a0791bfd9cfa mercurial/util.py
--- a/mercurial/util.py	Fri Jul 17 03:12:29 2020 +0200
+++ b/mercurial/util.py	Thu Jul 16 23:49:04 2020 +0200
@@ -1381,8 +1381,8 @@
 
 
 @contextlib.contextmanager
-def nullcontextmanager():
-    yield
+def nullcontextmanager(enter_result=None):
+    yield enter_result
 
 
 class _lrucachenode(object):