Skyrim mod error 16

This ate up time today, so I though I’d note it down here. All attempts to download Skyrim mods using the Steam Workshop were create error 16 unable to download file when starting the launcher. There’s barely anything on the internets about what causes this error, or how to fix it, so here’s my findings. To fix it in my case, I tried a number of things, but the only ones that ultimately produced a working download were to grant my user full control on the skyrim data directory, and to completely exit and restart steam. Which one of those actually did anything, I’m not sure. Probably this is as simple as “restart the steam client”…