Bug#595903: apt-setup: Fail to set up DVD as APT source during installation

[franco <orbital_arrow@yahoo.it>]

Be patient with me for my english. After done the minimal installation 
(by squeeze dvd medium 20100913), the installer does install nothing 
more, also after uncommenting the installation disk line in 
sources.list. I needed to end installation as it was, and rebooted the 
system with another bootloader from another partition. Trying to install 
remaining packages, aptitude ask to insert the dvd #1, so I do that, but 
installation fails with "file not found" error for each package. Noted 
that the disk were installed by aptitude on /media/apt, I unmounted it 
and remounted on /media/cdrom. Now the installation goes straight ahead. 
So the installer mounts the disk on one place but searches its contents 
on another.

Regards, Franco