I've downloaded the VarLogDistupgradeAptclone file in this bug report and restored it on an Ubuntu 16.04 system. I then ran do-release-upgrade without -proposed enabled and the upgrade failed to calculate. I then enabled -proposed and the upgrade path was calculated. Setting to verification-done.
I've downloaded the VarLogDistupgra deAptclone file in this bug report and restored it on an Ubuntu 16.04 system. I then ran do-release-upgrade without -proposed enabled and the upgrade failed to calculate. I then enabled -proposed and the upgrade path was calculated. Setting to verification-done.