update test for metaconfig serialization

test/test_state.py

@@ -5,6 +5,7 @@ from tiramisu.setting import owners
 from tiramisu.storage import delete_session
 from tiramisu.error import ConfigError
 from pickle import dumps, loads
+from py.test import raises
 
 
 def return_value(value=None):
@@ -288,9 +289,7 @@ def test_state_metaconfig():
     conf2._impl_test = True
     meta = MetaConfig([conf1, conf2], session_id='29090937')
     meta._impl_test = True
-    a = dumps(meta)
-    q = loads(a)
-    _diff_conf(meta, q)
+    raises(ConfigError, "dumps(meta)")
     try:
         delete_session('29090935')
         delete_session('29090936')