Comment 8 for bug 1796940

I've verified this fix on Ubuntu 16.04 LTS.

(xenial-amd64)root@impulse:/home/bdmurray# apt-cache policy ubuntu-release-upgrader-core
ubuntu-release-upgrader-core:
  Installed: 1:16.04.30
  Candidate: 1:16.04.30
  Version table:
 *** 1:16.04.30 500
        500 http://ubuntu.osuosl.org/ubuntu xenial-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     1:16.04.29 500
        500 http://ubuntu.osuosl.org/ubuntu xenial-updates/main amd64 Packages
     1:16.04.25 500
        500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
     1:16.04.12 500
        500 http://ubuntu.osuosl.org/ubuntu xenial/main amd64 Packages

(xenial-amd64)root@impulse:/home/bdmurray# do-release-upgrade
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [819 B]
Get:2 Upgrade tool [1242 kB]
Fetched 1243 kB in 0s (0 B/s)
authenticate 'bionic.tar.gz' against 'bionic.tar.gz.gpg'
extracting 'bionic.tar.gz'