Dear Maintainer,

After upgrading a Wheezy system to Jessie it fails to boot. Symptom is that
as soon as the BIOS hands over control to the boot loader it restarts without
screen output that I can see.

Eyeballing /etc/default/grub revealed that the GRUB_SERIAL_COMMAND line included
--speed=0, which is an error, but which worked OK with the Wheezy version of
grub (at least in that it did not prevent the boot).

So I would understand if you decide not to fix this, in which case the added
value of this report is that it will hopefully help others to fix their
systems if they happen to run into this as well.

So the fix I applied was to change the --speed parameter to 9600 and now the
system boots.