--- a/mercurial/fileset.py	Sat May 06 04:51:25 2017 +0530
+++ b/mercurial/fileset.py	Fri Feb 10 16:56:29 2017 -0800
@@ -37,7 +37,7 @@
     "end": (0, None, None, None, None),
 }
 
-keywords = set(['and', 'or', 'not'])
+keywords = {'and', 'or', 'not'}
 
 globchars = ".*{}[]?/\\_"