rbalint, in the output there is some oddity:
"Keeping auto-removable linux-image-extra-4.8.0-54-generic package(s) because it would also remove the following packages which should be kept in this step: libpam-systemd libsystemd0 libudev1 systemd systemd-sysv udev
(Reading database ... 53554 files and directories currently installed.)
Removing linux-image-extra-4.8.0-54-generic (4.8.0-54.57~16.04.1) ..."
So it says it is keeping linux-image-extra-4.8.0-54-generic and right thereafter it is removing the same package.
rbalint, in the output there is some oddity: extra-4. 8.0-54- generic package(s) because it would also remove the following packages which should be kept in this step: libpam-systemd libsystemd0 libudev1 systemd systemd-sysv udev extra-4. 8.0-54- generic (4.8.0- 54.57~16. 04.1) ..."
"Keeping auto-removable linux-image-
(Reading database ... 53554 files and directories currently installed.)
Removing linux-image-
So it says it is keeping linux-image- extra-4. 8.0-54- generic and right thereafter it is removing the same package.