Return whether the dev configuration directory should used.

def use_dev_config_dir(use_dev_config_dir=USE_DEV_CONFIG_DIR):
    """Return whether the dev configuration directory should used."""
    if use_dev_config_dir is not None:
        if use_dev_config_dir.lower() in {'false', '0'}:
            use_dev_config_dir = False
    else:
        use_dev_config_dir = DEV or not is_stable_version(__version__)
    return use_dev_config_dir