--- a/mercurial/help.py	Fri Dec 28 17:33:13 2018 -0500
+++ b/mercurial/help.py	Fri Dec 28 17:45:27 2018 -0500
@@ -119,7 +119,6 @@
     TOPIC_CATEGORY_CONCEPTS: 'Concepts',
     TOPIC_CATEGORY_MISC: 'Miscellaneous',
     TOPIC_CATEGORY_NONE: 'Uncategorized topics',
-    TOPIC_CATEGORY_NONE: 'Uncategorized topics',
 }
 
 def listexts(header, exts, indent=1, showdeprecated=False):