Should the doctor throw in production mode instead of printing warnings about untool

[dmbch]

Since we always validate everything and some issues untool warns about are very much use-case specific, I would prefer not to throw exceptions if we do not have to.

E.g.: while I think it is valid to warn about a serve specific misconfiguration during a build, I do not think it is appropriate to throw, i.e. crash. In fact, I would prefer only crashing if absolutely necessary and recovering whenever possible.

If we do crash, however, I think we ought to provide as much context/info as possible, allowing our users to make a connection from crash to warning.

[ZauberNerd]

Fine for now. Maybe we can rethink this as part of Hops 12 / 13.