The cargo-semver-checks cache key starts with a dash, like -semver-<whatever> and the gh actions-cache delete command was treating it as a flag, which it did not recognize. Hopefully by passing the key after -- will force it to treat it positionally.
cc @obi1kenobi - you might be interested to know that the leading dash in the cargo-semver-checks cache key can be a footgun for automated tooling.
Originally posted by @davidhewitt in https://github.com/PyO3/pyo3/pull/3970
We should remove the leading dash from our cache keys. I don't recall adding it there on purpose.