Hello, I am developing a module in Odoo 8 and I want to display a message when a value field changes. In this case, I want to display a warning message when the pricelist associated with a sale order changes. This is my code:

class sale_order(models.Model):
    _inherit = 'sale.order'

    @api.onchange('pricelist_id')
    def test_change(self):
        return {
        'warning': {
            'title': "test",
            'message': "testing",
            }
        }

I can install the module correctly, but when I change the pricelist selection in sale.order.form, there isn't any warning message. Why?

Thanks!