Some experiencing this bug could test the the theory by editing the file DistUpgradeCache.py in /tmp/ubuntu-release-upgrader-TMPNAME and then cd'ing into that directory and running sudo ./trusty and seeing if they get the same traceback.
Some experiencing this bug could test the the theory by editing the file DistUpgradeCache.py in /tmp/ubuntu- release- upgrader- TMPNAME and then cd'ing into that directory and running sudo ./trusty and seeing if they get the same traceback.