Unfortunately not just a simple Rakefile patch...
The kubeyaml situation changed a bit at the new version has been re-written as a react app without a CLI.
We could probably stick to the old implementation and maintain future updates (for each k8s version) ourselves, but that does not sound very appealing.
I had a bookmark for https://github.com/instrumenta/kubeval in my browser (that's all the research I did on that by now). If it does what we need/got from kubeyaml, we can maybe migrate with less effort then patching kubeyaml.