Arvados

If arvados-client diagnostics skips the arvados-server health check, it reports this at the info level. This is relatively easy to miss if you're not specifically looking for it, it looks basically just like everything else.

If you run arvados-client diagnostics so it tries to build a diagnostics image (the default), and it can't run Docker, it reports an error.

IMO the behavior should be:

• Any skipped checks are reported as warnings.
• Consider an option to promote those to errors.
• If you pass -docker-image or -docker-image-from, that check runs exactly as requested and reports an error if it fails.
• If you pass neither, the behavior is: it tries to build a diagnostic image, and if the image build fails, it reports a skipped check and falls back to running the check with the hello-world image.