It is no bug but a type mistake
select the correct Port from the Tools menu then open the Serial Monitor to view the debug messages. Note: the default Baud Rate for MySensors is 112500
This to your information
Thanks for reporting this @TON-RIJNAARD, much appreciated.
Where did you find the mistake? Was it in a Sketch? If so, which sketch? Was it on a page? If so which page?
It is on this page
Build and upload the sketch with the above debug flag enabled in MyConfig.h.
Keep the sensor connected to your computer and enable the Serial Monitor in the Arduino IDE. Tools>Serial Monitor.
Set the baud-rate to 115200.
@TON-RIJNAARD Thanks! I have fixed the page, it now says 115200.