update serializers

tests/integration/test_register_serializer.py

@@ -10,7 +10,7 @@ class MockSerializer(object):
     def deserialize(self, cassette_string):
         self.serialize_count += 1
         self.cassette_string = cassette_string
-        return []
+        return {'interactions':[]}
 
     def serialize(self, cassette_dict):
         self.deserialize_count += 1