Replace pkg/errors with standard library functions

[twz123]

No description provided.

[twz123]

The copyright check seems to fail when it shouldn't? 🤔

pkg/cluster/cluster.go: Warning: a newly introduced file contains an old copyright
pkg/cluster/key_store.go: Warning: a newly introduced file contains an old copyright
pkg/cluster/machine.go: Warning: a newly introduced file contains an old copyright
pkg/exec/local.go: Missing SPDX license identifier
pkg/exec/local.go: Missing or incorrect copyright boilerplate
gh: Not Found (HTTP 404)
{"message":"Not Found","documentation_url":"https://docs.github.com/rest"}Failed to add a github annotation to file: pkg/exec/local.go
* 1 files are missing or have incorrect copyright boilerplate

[kke]

For the first few, I guess it lost track of file history somehow, but those are just Warnings.

pkg/exec/local.go: Missing or incorrect copyright boilerplate The boilerplate checker script .github/scripts/check_boilerplate.sh only ignores the kubernetes authors header in pkg/docker. I don't know why it didn't complain before.

[twz123]

Maybe something like #74 might help?