Comment 1 for bug 1494628

Well, I couldn't sleep and decided to work on this, found a simple solution ;-)

My branch should prevent this situation from happening again, however to fix your existing request in an inconsistent state, you'll need to manually set the siloname field in bileto to ubuntu/landing-NNN and then it should work just fine, from there you can either free it (since you already have the identical other one) or use it.