diff -r 2279d90eed9a -r 077301ac69dc mercurial/scmutil.py
--- a/mercurial/scmutil.py	Fri Jun 29 14:14:35 2018 -0700
+++ b/mercurial/scmutil.py	Fri Jun 29 14:43:41 2018 -0700
@@ -1328,7 +1328,7 @@
         self.total = total
 
     def __enter__(self):
-        pass
+        return self
 
     def __exit__(self, exc_type, exc_value, exc_tb):
         self.complete()