Print a value for the specified key. If key is not found xon_db exists with code 1.

def get(file_name, key):
    """
    Print a value for the specified key. If key is not found xon_db exists with code 1.
    """
    db = XonoticDB.load_path(file_name)
    value = db.get(key)
    if value is None:
        sys.exit(1)
    else:
        click.echo(value)