The gotest.tools `fs.NewDir` utility already sets up a `t.Cleanup`,
so we can treat it the same as `t.TempDir()` and let it handle
cleaning up by itself.
We should probably consider replacing some of this with `t.TempDir`.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
While there may be reasons to keep pkg/errors in production code,
we don't need them for these tests.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>