Rails deployment fails: "Error failed to fetch an image or build from source: error building: unexpected EOF"

I can’t yet tell if the deploy’s going to work all the way through, but I got past the error by running everything from a linux partition on a separate computer: my original computer that didn’t work was running windows subsystem for linux (WSL). If this turns out to be my workflow, it’ll be a bit of a pain but at least it’s possible.