Should not allow impossible release upgrades

[Doug McMahon]

For example now in 14.04 it will show & will attempt a 14.04 to 15.10 upgrade. This upgrade is impossible & the attempt will result in a destroyed 14.04 install.
The app should not show this upgrade let alone allow it to be done (not actually 'done' as it will fail hard during the install phase.

[Brian Murray (brian-murray)]

Could you provide some details about how this is impossible / and or how a system was destroyed?

[Doug McMahon (mc3man)]

Sure - as it happens I was just putting in a new 14.04.3 install when email arrived so -
Upgraded the install
Opened up software properties & set it to Notify me 'For any new version'

A bit later update-manager? notified me of a distribution upgrade so went ahead with it, ie. an upgrade to 15.10
It proceeded along until about 1/3 of the way thru installing packages, crashed to a black screen & no longer can be booted to.
I can access any logs & attach, the /var/log/dist-upgrade/*.logs may be appropriate, the apt.log is 92 kB, the apt-term.log is 376kB, the main.log is only 46kB. Do you want them & if so should I compress?
Will attach a few screens