Comment 10 for bug 1490990

It's not clear multiple configuration directories were ever supported. The --config-file option can be repeated with multiple files, but the --config-dir option seems to want just one value, as indicated in the code and the help string. So this may be a misunderstanding of intent. It probably makes sense to support multiple directories, for the use case described here, so we should give some thought to how to do that. The docstring for ConfigDirAction makes me think it is expecting to be used more than once, so perhaps the setattr() can be replaced with some more complicated logic to extend the path. OTOH, that would change the type of the config_dir value in the namespace, so it might actually be better to add a new --config-path option that can be used to set multiple values and to eventually deprecate the current --config-dir option.