I wanted to follow up on this in case it helps anyone else.
I tried manually scraping it off, with the Python running to suck up the scrapings, but it was back again within the week, including spreading over the gravel.
In the end I did two things. One, repeat the scraping and water change but then dosed Boyd Chemiclean cyanobacteria aquarium treatment, found on Amazon. Just followed the dosing direction on the box, and repeated water change after 2 days as instructed. Two, I added a powerhead to increase flow, and directed it across the driftwood that had the worst of it.
It's been a couple of weeks, and so far the aquarium is looking much improved. There is some algae growing, but as far as I can see the cyanobacteria is gone.