QDBusMessage

This was done in https://github.com/fluxer/katie/commit/c85de19451c95a515b4406039fe61dfd4cfabcc6. The setDelayedReply() method of QDBusMessage cannot be const because it is setter.

No source compatible methods are in place because you should evaluate how to handle this in your projects. For an example:

void sendError(const QDBusMessage &msg)
{
    msg.setDelayedReply(true);
    QDBusConnection::sessionBus()
        .send(msg.createErrorReply("local.AnErrorName", "You've got an error!"));
}

Should be changed to:

void sendError(const QDBusMessage &msg)
{
    QDBusMessage msgcopy(msg);
    msgcopy.setDelayedReply(true);
    QDBusConnection::sessionBus()
        .send(msgcopy.createErrorReply("local.AnErrorName", "You've got an error!"));
}