You can not debug the server code in developer mode. Actually, if you need to debug the server code, you need to restart the server with the --debug option. In order to do that, you need to have access to the server console and be able to insert the

import pdb;pdb.set_trace()

statement in the module you need to debug

This is a duplicate answer for your frist ask:

https://accounts.openerp.com/forum/Help-1/question/83

No, you can't debug python code via web client. You must use python print and pdb functions.