enh: fail fast when we can't find yml files

[lwasser]

There are selveral instances when a packages or contributors.yml file may not be found. Most recently it wasn't found because I redid the website and we moved from a _data/ to data/ directory path. And that killed our workflows.

While we don't anticipate this happening often it could happen via a github availability glitch or a path change and so in that case we should likely always fail early and fast.

Let's implement a more project wide approach that ensures we fail fast given we use those files in multiple entry points and overwrite them via a pr in a github action!

[lwasser]

To add to this issue, you can see what happens when the files are not found here:
https://github.com/pyOpenSci/pyosMeta/actions/runs/31519097712 !! so it will be good to add these checks for when the data are missing and a 404 is returned.