Display concerned object when no plugin can be applied.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@16621 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/Core/Folder.py

@@ -508,7 +508,7 @@ class Folder(CopyContainer, CMFBTreeFolder, CMFHBTreeFolder, Base, FolderMixIn,
           self._folder_handler = "%r" % plugin
           break
       if self._folder_handler is None:
-        raise ValueError, 'No plugin defined'
+        raise ValueError, 'No plugin defined on %r' % (self, )
       
   def newContent(self, *args, **kw):
     """ Create a new content """