load json file and check file content format

def load_json_file(json_file):
    """ load json file and check file content format
    """
    with io.open(json_file, encoding='utf-8') as data_file:
        try:
            json_content = json.load(data_file)
        except exceptions.JSONDecodeError:
            err_msg = u"JSONDecodeError: JSON file format error: {}".format(json_file)
            logger.log_error(err_msg)
            raise exceptions.FileFormatError(err_msg)

        _check_format(json_file, json_content)
        return json_content