fileset: handle error of string unescaping

mercurial/fileset.py

@@ -54,7 +54,7 b' def tokenize(program):'
                 c = program[pos]
                 decode = lambda x: x
             else:
-                decode = lambda x: x.decode('string-escape')
+                decode = parser.unescapestr
             pos += 1
             s = pos
             while pos < l: # find closing quote

tests/test-fileset.t

@@ -49,6 +49,9 b' Test operators and basic patterns'
   $ fileset 'a* - a1'
   a2
   $ fileset 'a_b'
+  $ fileset '"\xy"'
+  hg: parse error: invalid \x escape
+  [255]
 
 Test files status