It turns out that the problem was that the poll had been duplicated in a quote block, and the migration didn’t know to ignore it. It was in a PM, apparently as an example of how polls worked. I deleted the duplicate and the migration ran fine.
It turns out that the problem was that the poll had been duplicated in a quote block, and the migration didn’t know to ignore it. It was in a PM, apparently as an example of how polls worked. I deleted the duplicate and the migration ran fine.