py3: fix mixed bytes/unicode in revsetlang._aliassyminitletters

mercurial/revsetlang.py

@@ -473,7 +473,7 b' def optimize(tree):'
 
 # the set of valid characters for the initial letter of symbols in
 # alias declarations and definitions
-_aliassyminitletters = _syminitletters | set(pycompat.sysstr('$'))
+_aliassyminitletters = _syminitletters | {'$'}
 
 def _parsewith(spec, lookup=None, syminitletters=None):
     """Generate a parse tree of given spec with given tokenizing options