Comment 2 for bug 1671468

Right, the idea was to replace excuse.is_valid with something like excuse.current_verdict. britney already has the policy_verdict local variable in should_upgrade_src() which contains what we need, it just needs to move into the Excuse object. Preferrably it should replace excuse.is_valid to avoid redundancy, or is_valid could maybe become a property which is true iff self.policy_verdict not in [PolicyVerdict.REJECTED_PERMANENTLY, PolicyVerdict.REJECTED_TEMPORARILY]