Raise NotImplementedError when not implemented.

git-svn-id: https://svn.erp5.org/repos/neo/branches/prototype3@45 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/client/app.py

@@ -461,7 +461,7 @@ class Application(object):
             self._clear_txn()
 
     def loadBefore(self, oid, tid):
-        pass
+        raise NotImplementedError
 
     def undo(self, transaction_id, txn):
         if transaction is not self.txn: