Comment 3 for bug 307269

Both issues observed here (the duplicate launchpad/trunk tasks, and the declined distroseries nominations where distroseries tasks exist already) are possible because BugNomination.{approve,decline} do not respect their documentation from IBugNomination. IBugNomination states that approving an approved nomination is a no-op, and declining an approved one raises an exception. However, the implementation in BugNomination doesn't perform those checks.

This means that one can decline a nomination after it has been approved, resulting in those extra distroseries nominations. A further approval of a distroseries nomination crashes because it would create a duplicate bugtask. However, there is a missing UNIQUE index (bug #417636) which allows an approved then declined productseries nomination to be successfully approved again, creating the duplicate launchpad/trunk task as seen above.

I've fixed BugNomination.{approve,reject} to make these situations impossible in my bug nomination export branch, but an attempt to decline an existing task through the web UI will start to OOPS.