Fix generating of sre_constants.h on Python 3.

Lib/sre_constants.py

@@ -219,8 +219,7 @@ SRE_INFO_CHARSET = 4 # pattern starts with character from given set
 
 if __name__ == "__main__":
     def dump(f, d, prefix):
-        items = d.items()
-        items.sort(key=lambda a: a[1])
+        items = sorted(d.items(), key=lambda a: a[1])
         for k, v in items:
             f.write("#define %s_%s %s\n" % (prefix, k.upper(), v))
     f = open("sre_constants.h", "w")