def file_config(filename=None):
    """Returns the config values found in a configuration file.

    Args:
        filename (str): the JSON file with the configuration values.
            If ``None``, CONFIG_DEFAULT_PATH will be used.

    Returns:
        dict: The config values in the specified config file (or the
              file at CONFIG_DEFAULT_PATH, if filename == None)
    """
    logger.debug('On entry into file_config(), filename = {}'.format(filename))

    if filename is None:
        filename = CONFIG_DEFAULT_PATH

    logger.debug('file_config() will try to open `{}`'.format(filename))
    with open(filename) as f:
        try:
            config = json.load(f)
        except ValueError as err:
            raise exceptions.ConfigurationError(
                'Failed to parse the JSON configuration from `{}`, {}'.format(filename, err)
            )

        logger.info('Configuration loaded from `{}`'.format(filename))

    return config
Returns the config values found in a configuration file.

    Args:
        filename (str): the JSON file with the configuration values.
            If ``None``, CONFIG_DEFAULT_PATH will be used.

    Returns:
        dict: The config values in the specified config file (or the
              file at CONFIG_DEFAULT_PATH, if filename == None)