@strickce's formal bug report to the IDE developers is here:
Thanks for bringing that to our attention!
I think there is an important comment in that issue:
if I stop the serial monitor and restart it, the error message goes away.
If I understand correctly, the problem is that the Serial Monitor is handling the network port selection incorrectly. It is normal (though perhaps not ideal UX?) that if you have Serial Monitor open and disconnect the serial port (e.g., unplug the Arduino board USB cable from your computer), then you get these repeated notifications about the failure to reconnect to the serial port. Like this:
