Comment 202 for bug 1289977

IMHO, that bug simply shows that dist-upgrade breaks the boot by blindly (re)installing GRUB whatever the boot setup is.
In other words, dist-upgrade does not support enough boot configurations.

A very simple and quick fix is: dist-upgrade should not install any bootloader. (why taking the risk of breaking the boot?)

Plus, there are probably several sub-bugs (several types of "unsupported configurations" leading to the same error message) mixed in that report, would be easier to understand if each user was creating his own report, then devs could regroup them into categories.