Implement __len__, __getitem__, __getslice__.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@23560 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/Message.py

@@ -140,6 +140,15 @@ class Message(Persistent):
       message = message.decode('utf-8')
     return message
 
+  def __len__(self):
+    return len(str(self))
+
+  def __getitem__(self, index):
+    return str(self)[index]
+
+  def __getslice__(self, i, j):
+    return str(self)[i:j]
+
 InitializeClass(Message)
 allow_class(Message)