You can debug using cmd in windows enter with cmd into odoo.exe folder C:\Program Files (x86)\Odoo 8.0-20150719\server and execute this command
odoo --log-level=debug
or terminal in Linux enter with terminal into odoo.py file (/usr/bin/) and execute this command
python odoo.py --log-level=debug
tape ctrl+z or ctrl+c to desactivate a log .
You will find a file (openerp-server.log) in /var/log/odoo/