Comment 6 for bug 1828072

I tested this when upgrading from bionic to cosmic and it also passed the test.

root@clean-bionic-amd64:/tmp/ubuntu-release-upgrader-z0ltcdq5# head -n10 /var/log/dist-upgrade/main.log
2019-05-09 14:51:06,729 INFO Using config files '['./DistUpgrade.cfg']'
2019-05-09 14:51:06,729 INFO uname information: 'Linux clean-bionic-amd64 4.15.0-47-generic #50-Ubuntu SMP Wed Mar 13 10:44:52 UTC 2019 x86_64'
2019-05-09 14:51:07,065 INFO apt version: '1.6.10'
2019-05-09 14:51:07,066 INFO python version: '3.6.7 (default, Oct 22 2018, 11:32:17)
[GCC 8.2.0]'
2019-05-09 14:51:07,069 INFO release-upgrader version '18.10.11.7' started
2019-05-09 14:51:07,079 INFO locale: 'en_US' 'UTF-8'
2019-05-09 14:51:07,150 DEBUG setting up environ for non-interactive use
2019-05-09 14:51:07,266 DEBUG Using 'DistUpgradeViewNonInteractive' view
2019-05-09 14:51:07,301 DEBUG enable dpkg --force-overwrite
root@clean-bionic-amd64:/tmp/ubuntu-release-upgrader-z0ltcdq5# grep -i "obsoletekernel" /var/log/dist-upgrade/main.log
2019-05-09 15:04:52,807 DEBUG identifyObsoleteKernels()
2019-05-09 15:04:58,059 DEBUG identifyObsoleteKernels found '{'linux-modules-extra-4.15.0-45-generic', 'linux-image-4.15.0-48-generic', 'linux-headers-4.15.0-46-generic', 'linux-headers-4.15.0-45-generic', 'linux-modules-4.15.0-46-generic', 'linux-modules-4.15.0-48-generic', 'linux-modules-extra-4.15.0-46-generic', 'linux-modules-extra-4.15.0-48-generic', 'linux-modules-4.15.0-45-generic', 'linux-image-4.15.0-45-generic', 'linux-headers-4.15.0-48-generic', 'linux-image-4.15.0-46-generic'}'