Bug#681227: installation-reports: grub-install tries to install to a nonsense string

[willem kuyn <willemkuyn@gmail.com>]

Hi,

I tried to reproduce the bug in different settings.
- A virtual machine installation: grub always writes to /dev/sda
- A new lenova laptop booting from dvd: grub writes to /dev/sda
- Installation on an external usb disk: grub writes to /dev/sda
	This is the original disk in the machine, while it was my
	expectation that grub should write to the MBR of usb disk.
	Booting from the usb disk is not possible only via /dev/sda.

The question is:
What is the configuration where grub writes to the MBR of /dev/sdb?

Willem