Unfortunately, `go get` rejects repos that have files with ':':
https://github.com/golang/go/issues/28001.
We have one such file in the tests.
This prevents some of the Go tooling from working on the latest release,
including pkg.go.dev.
So, as a workaround we use a compatible file name in the repository, and
rename it when running the test. This is very hacky, but it's okay for a
single test.