Popup like warning message with Continue/Cancel button that would eventually rollback action

Hello,

Currently this is impossible in OpenERP to show the user a popup with a warning where the user could either
1) Continue
2) Cancel action

Cancelling would behave pretty like osv.except_osv , rolling back the action but without error message then.

This pattern is especially useful when the we need to warn the user about option he choosed when saving a record for instance or doing some risky action. Like: "Selling product with price 1 euro will likely fuck up totally your margin, do you really wanna freak with me? Continue | Cancel"

Hope we can have an easy API pattern for this kind of popups.