ARGOMENTO: BOTTONE ANNULLA SU ORDINI DI ACQUISTO

            for inv in purchase.invoice_ids:
                if inv and inv.state not in ('cancel','draft'):
                    raise osv.except_osv(
                        _('Unable to cancel this purchase order.'),
                        _('You must first cancel all receptions related to this purchase order.'))
                if inv:
                    wf_service.trg_validate(uid, 'account.invoice', inv.id, 'invoice_cancel', cr)
            self.pool['purchase.order.line'].write(cr, uid, [l.id for l in  purchase.order_line],
                    {'state': 'cancel'})
        # [antoniov: 2015-11-12] cancel did not work, added write
        self.write(cr,uid,ids,{'state':'cancel'})

    def action_cancel(self, cr, uid, ids, context=None):
        for purchase in self.browse(cr, uid, ids, context=context):
            for pick in purchase.picking_ids:
                for move in pick.move_lines:
                    if pick.state == 'done':
                        raise osv.except_osv(
                            _('Unable to cancel the purchase order %s.') % (purchase.name),
                            _('You have already received some goods for it.  '))
            self.pool.get('stock.picking').action_cancel(cr, uid, [x.id for x in purchase.picking_ids if x.state != 'cancel'], context=context)
            for inv in purchase.invoice_ids:
                if inv and inv.state not in ('cancel', 'draft'):
                    raise osv.except_osv(
                        _('Unable to cancel this purchase order.'),
                        _('You must first cancel all invoices related to this purchase order.'))
            self.pool.get('account.invoice') \
                .signal_workflow(cr, uid, map(attrgetter('id'), purchase.invoice_ids), 'invoice_cancel')
            # qui dovrebbe essere inserita la patch
        self.signal_workflow(cr, uid, ids, 'purchase_cancel')
        return True