Need help; how to use apt/dpkg to upgrade mounted filesystem using chroot.

[John Foster <jfoster@augustmail.com>]

Here is what I want to do; I have a dual boot system with partitions:
/stable and /unstable. I want to mount /unstable to directory
/stable/unstable  after doing so I issue command; 
'chroot /unstable apt-get update'
'chroot /unstable apt-get upgrade'

What happens is that all of the proper files on /unstable are downloaded
and cached in /unstable/var/cache/apt/archives...so far, so good. Then I
get an error message saying

E: Failure running script /usr/bin/apt-listchanges --apt || test $? -ne
10

I tried doing 'cd /unstable' then 'chroot . bin/bash' and issueing all
of the previous commands from within the shell. I got the same errors.
I tried removing apt-listchanges, but I can not. Postremoval scripts
fail.
I think there must be some way to do what I want, but I have not been
able to find any reference to this. One listmember suggested using dpkg
but I was unable to get that to work. It will unpack the downloaded
files, but will not configure them.
Thanks.
John