Replaced cPickle import with six.moves.cPickle (#3858)

frappe/utils/redis_wrapper.py

@@ -3,7 +3,7 @@
 from __future__ import unicode_literals
 
 import redis, frappe, re
-import cPickle as pickle
+from six.moves import cPickle as pickle
 from frappe.utils import cstr
 from six import iteritems