Configure the root logger and a logfile handler.

    Args:
        log_level: The logging level to set the logger handler.

def enable_logging(log_level):
    # type: (typing.Union[None, int]) -> None
    """Configure the root logger and a logfile handler.

    Args:
        log_level: The logging level to set the logger handler.
    """
    root_logger = logging.getLogger()
    root_logger.setLevel(logging.DEBUG)
    logfile_handler = logging.StreamHandler(_LOGFILE_STREAM)
    logfile_handler.setLevel(logging.DEBUG)
    logfile_handler.setFormatter(logging.Formatter(
        '%(levelname)s [%(asctime)s][%(name)s] %(message)s'))
    root_logger.addHandler(logfile_handler)
    if signal.getsignal(signal.SIGTERM) == signal.SIG_DFL:
        signal.signal(signal.SIGTERM, _logfile_sigterm_handler)
    if log_level:
        handler = logging.StreamHandler()
        handler.setFormatter(_LogColorFormatter())
        root_logger.setLevel(log_level)
        root_logger.addHandler(handler)