def on_cleanup_error(function, path, excinfo):
                click.secho("warning: failed to remove file or directory: {}\n"
                            "please delete it manually.".format(path),
                            fg="red")
def serialize(self, value, display=False):
        if not value:
            return ""
        return "\n  " + "\n  ".join(encode(v) for v in value if v)