--- a/mercurial/upgrade_utils/actions.py	Fri Jul 16 14:22:02 2021 +0200
+++ b/mercurial/upgrade_utils/actions.py	Mon Jun 28 12:12:34 2021 +0200
@@ -633,7 +633,10 @@
     newactions = []
 
     for d in format_upgrades:
-        name = d._requirement
+        if util.safehasattr(d, '_requirement'):
+            name = d._requirement
+        else:
+            name = None
 
         # If the action is a requirement that doesn't show up in the
         # destination requirements, prune the action.