It seems one can't overwrite a cache entry:
```
Failed to save: Unable to reserve cache with key linkcheck--0.8.1, another job may be creating this cache. More details: Cache already exists. Scope: refs/heads/master, Key: linkcheck--0.8.1, Version: 33f8fd511bed9c91c40778bc5c27cb58425caa894ab50f9c5705d83cb78660e0
Warning: Cache save failed.
```
A proper solution is to use `restore-keys`:
https://github.com/actions/cache/blob/main/tips-and-workarounds.md#update-a-cache
This will cause the CI build to be marked successful even if the build
failed. Instead, use `if: '!cancelled()'` to always save the cache
(except when the job is cancelled), even if the linkcheck failed.
See https://stackoverflow.com/a/58859404 for more.
It's super annoying to be forced to use this bad convention, and
apparently everyone agrees. The only reason no improvements have been
done is because those were blocked on writing a better checker.
I strongly believe that no checker is better than a bad checker, so
let's just delete it in the meantime. I kindly asked anyone who sees
this to complain about overly long sentences in review in the future, I
think we can make this turn out fine.
Eric Huss
Jakub Beránek
Martin Liska
Noah Lev
Nilstrieb
Yuki Okushi
jyn
Niko Matsakis
Tshepang Lekhonkhobe
Yuki Okushi