Fix error with reraising exceptions in serializer

nilmdb/utils/serializer.py

@@ -63,7 +63,7 @@ def serializer_proxy(obj_or_type):
             if exc_info is None:
                 return result
             else:
-                raise exc_info[0](exc_info[1]).with_traceback(exc_info[2])
+                raise exc_info[1].with_traceback(exc_info[2])
 
     class SerializerObjectProxy(object):
         def __init__(self, obj_or_type, *args, **kwargs):