Write a DEBUG log file COMMAND-YYYYMMDD-HHMMSS.ffffff.log.

def write_logfile():
    # type: () -> None
    """Write a DEBUG log file COMMAND-YYYYMMDD-HHMMSS.ffffff.log."""
    command = os.path.basename(os.path.realpath(os.path.abspath(sys.argv[0])))
    now = datetime.datetime.now().strftime('%Y%m%d-%H%M%S.%f')
    filename = '{}-{}.log'.format(command, now)
    with open(filename, 'w') as logfile:
        if six.PY3:
            logfile.write(_LOGFILE_STREAM.getvalue())
        else:
            logfile.write(_LOGFILE_STREAM.getvalue().decode(  # type: ignore
                errors='replace'))