def get_config(self, key, default=MISSING):
        """Get the value of a persistent config key from the registry

        If no default is specified and the key is not found ArgumentError is raised.

        Args:
            key (string): The key name to fetch
            default (string): an optional value to be returned if key cannot be found

        Returns:
            string: the key's value
        """

        keyname = "config:" + key

        try:
            return self.kvstore.get(keyname)
        except KeyError:
            if default is MISSING:
                raise ArgumentError("No config value found for key", key=key)

            return default
Get the value of a persistent config key from the registry

        If no default is specified and the key is not found ArgumentError is raised.

        Args:
            key (string): The key name to fetch
            default (string): an optional value to be returned if key cannot be found

        Returns:
            string: the key's value