[python3] Use pickle instead of cPickle in Python3

gridtk/models.py

@@ -5,8 +5,13 @@ from sqlalchemy.orm import backref
 from sqlalchemy.ext.declarative import declarative_base
 
 import os
+import sys
+
+if sys.version_info[0] >= 3:
+  from pickle import dumps, loads
+else:
+  from cPickle import dumps, loads
 
-from cPickle import dumps, loads
 from .tools import logger
 
 Base = declarative_base()
@@ -261,4 +266,4 @@ def add_job(session, command_line, name = 'job', dependencies = [], array = None
 
   session.commit()
 
-  return job
\ No newline at end of file
+  return job