Comment 8 for bug 1828072

And an upgrade from Bionic to Disco also passed:

root@clean-bionic-amd64:/tmp/ubuntu-release-upgrader-bctl6u37# head -n10 /var/log/dist-upgrade/main.log
2019-05-09 16:02:07,695 INFO Using config files '['./DistUpgrade.cfg.bionic']'
2019-05-09 16:02:07,695 INFO uname information: 'Linux clean-bionic-amd64 4.15.0-48-generic #51-Ubuntu SMP Wed Apr 3 08:28:49 UTC 2019 x86_64'
2019-05-09 16:02:08,038 INFO apt version: '1.6.10'
2019-05-09 16:02:08,038 INFO python version: '3.6.7 (default, Oct 22 2018, 11:32:17)
[GCC 8.2.0]'
2019-05-09 16:02:08,040 INFO release-upgrader version '19.04.16.4' started
2019-05-09 16:02:08,047 INFO locale: 'en_US' 'UTF-8'
2019-05-09 16:02:08,116 DEBUG setting up environ for non-interactive use
2019-05-09 16:02:08,158 DEBUG Using 'DistUpgradeViewNonInteractive' view
2019-05-09 16:02:08,194 DEBUG enable dpkg --force-overwrite
root@clean-bionic-amd64:/tmp/ubuntu-release-upgrader-bctl6u37# grep -i obsoletekernels /var/log/dist-upgrade/main.log
2019-05-09 16:19:00,748 DEBUG identifyObsoleteKernels()
2019-05-09 16:19:05,646 DEBUG identifyObsoleteKernels found '{'linux-headers-4.15.0-46-generic', 'linux-image-4.15.0-45-generic', 'linux-modules-4.15.0-45-generic', 'linux-image-4.15.0-46-generic', 'linux-modules-extra-4.15.0-45-generic', 'linux-headers-4.15.0-45-generic', 'linux-modules-extra-4.15.0-47-generic', 'linux-modules-4.15.0-46-generic', 'linux-modules-extra-4.15.0-46-generic', 'linux-image-4.15.0-47-generic', 'linux-modules-4.15.0-47-generic', 'linux-headers-4.15.0-47-generic'}'