KOO 5.0.4 doesn't show wizard exceptions

[José Pastor]

In my installation with OpenERP Server 5.0.16, when a wizard raise exception, Koo doesn't show in screen.

Sample:
if invoice.state in ['draft', 'proforma2', 'cancel']:
     raise wizard.except_wizard(_('Error !'), _('Can not pay draft/proforma/cancel invoice.'))

If you try pay invoice in draft, proforma2 or cancel status, messatge "Can not pay drat/proforma/cancel invoice" is showed in screen if you use OpenERP Client GTK or WebClient, but not in my Koo installation.