"failed retrieving file 'rutabaga-ffi-0.1.6-2-x86_64.pkg.tar.zst.sig'" error when booting a newly made .iso file

In #44 , I have a fork that lets me create an .iso from my local Omarchy build. I have some trivial changes (basically modifying the default packages that are installed). But when I use this CLI tool to try and *boot* the created .iso file, I get this error:

https://gist.github.com/c10r/1ee9dc021bda5b81c4b655b51723d5e4