--- a/mercurial/windows.py	Wed Dec 12 06:41:19 2018 +0100
+++ b/mercurial/windows.py	Sat Dec 15 01:26:18 2018 -0500
@@ -132,7 +132,10 @@
         self._fp = fp
 
     def __enter__(self):
-        return self._fp.__enter__()
+        self._fp.__enter__()
+        # Return this wrapper for the context manager so that the name is
+        # still available.
+        return self
 
     def __exit__(self, exc_type, exc_value, traceback):
         self._fp.__exit__(exc_type, exc_value, traceback)