diff -r 2959c3e986e0 -r bd872f64a8ba mercurial/dispatch.py
--- a/mercurial/dispatch.py	Sat May 06 04:51:25 2017 +0530
+++ b/mercurial/dispatch.py	Fri Feb 10 16:56:29 2017 -0800
@@ -749,7 +749,7 @@
     # imported and commands.table is populated.
     debugcommands.command
 
-    uis = set([ui, lui])
+    uis = {ui, lui}
 
     if req.repo:
         uis.add(req.repo.ui)