--- a/hgext/rebase.py	Wed Jul 19 13:17:49 2017 -0700
+++ b/hgext/rebase.py	Wed Apr 03 11:21:27 2019 -0700
@@ -1878,8 +1878,8 @@
     obsolete successors.
     """
     obsoletenotrebased = {}
-    obsoletewithoutsuccessorindestination = set([])
-    obsoleteextinctsuccessors = set([])
+    obsoletewithoutsuccessorindestination = set()
+    obsoleteextinctsuccessors = set()
 
     assert repo.filtername is None
     cl = repo.changelog