7.0 avoid recatching error in debug mode

Hi all
This change only impact OpenERP/Odoo when it's started in debug mode (so it's only usefull for dev)
The idea is to avoid the "recatch" of error when we start OpenERP in debug mode. It help me a lot to debug OpenERP so I share it (I remember some tricky bug, where view was corrupted after an update, as OpenERP was recatching the bug, it was imposible to understand without removing the recatch) . I do not ask a PR to official as OpenERP SA think it's useless (https://code.launchpad.net/~sebastien.beau/openobject-server/openobject-server-debug-mode/+merge/113996).

But if community is interrested than we can merge it. (If you have an other solution tell me)