It was the withdrawal agreement without the “political declaration”. Which mean that voting for it would have been like standing at the altar and pledging to love, honour and obey a man in a gorilla suit, while having no idea at all which man you’d see once the suit came off.
Here you go! OK, so it’s not quite a unicorn. It is, in fact, both a unicorn and not a unicorn. It’s a Schrodinger’s unicorn. Now you see it, now you don’t. Will that do?