This (with the line below) is now better, but it still means there's no default configuration. I'd prefer if this had some sort of sensible default, such as the previous system where it created a file in the same directory as config.yaml, corresponding to the cluster name. That might, in fact, be a reasonable choice here as well. If not, it needs error handling; with the present code it'll kill the whole script with KeyError if there's no _file configured.