invalid component gives unhelpful "unable to install" error

[matthiaskrgr]

if you pass an invalid --component, cbr will print a rather unhelpful message

            Err(InstallError::NotFound { .. }) => {
                // go back just one day, presumably missing a nightly
                nightly_date = nightly_date.pred();
                eprintln!(
                    "*** unable to install {}. roll back one day and try again...",
                    t
                );

instead of anything about missing components