import six package and update fix

Author: ericknavarro97

openpay/util.py

@@ -1,16 +1,15 @@
-
 import logging
 import sys
 
-from past.builtins import unicode
+import six
 
 logger = logging.getLogger('stripe')
 
 __all__ = ['utf8']
 
 
 def utf8(value):
-    if isinstance(value, unicode) and sys.version_info < (3, 0):
+    if isinstance(value, six.text_type) and sys.version_info < (3, 0):
         return value.encode('utf-8')
     else:
         return value