pasteurize should have imported chr from builtins for py23 compat

wetb/fast/fast_io.py

@@ -10,6 +10,7 @@ from __future__ import absolute_import
 from io import open
 from builtins import map
 from builtins import range
+from builtins import chr
 from future import standard_library
 standard_library.install_aliases()
 import os