QSerialPort prepends `/dev/cu.` to all serial port to be opened.

qDebug() << "SYS LOC:" << systemLocation;
descriptor = qt_safe_open(systemLocation.toLocal8Bit().constData(), flags);
qDebug() << "descriptor:" << descriptor;

SYS LOC: "/dev/cu./dev/ttys002" 
descriptor: -1 

#ifdef Q_OS_MAC
static const QString defaultFilePathPrefix = QStringLiteral("/dev/cu.");
static const QString unusedFilePathPrefix = QStringLiteral("/dev/tty.");
#else
static const QString defaultFilePathPrefix = QStringLiteral("/dev/");
#endif

QString QSerialPortPrivate::portNameToSystemLocation(const QString &port)
{
    QString ret = port;

#ifdef Q_OS_MAC
    ret.remove(unusedFilePathPrefix);
#endif

    if (!ret.contains(defaultFilePathPrefix))
        ret.prepend(defaultFilePathPrefix);
    return ret;
}