diff -r 2959c3e986e0 -r bd872f64a8ba mercurial/revsetlang.py
--- a/mercurial/revsetlang.py	Sat May 06 04:51:25 2017 +0530
+++ b/mercurial/revsetlang.py	Fri Feb 10 16:56:29 2017 -0800
@@ -44,9 +44,9 @@
     "end": (0, None, None, None, None),
 }
 
-keywords = set(['and', 'or', 'not'])
+keywords = {'and', 'or', 'not'}
 
-_quoteletters = set(['"', "'"])
+_quoteletters = {'"', "'"}
 _simpleopletters = set(pycompat.iterbytestr("():=,-|&+!~^%"))
 
 # default set of valid characters for the initial letter of symbols