daily upgrade on 16.04 hangs

doing a regular upgrade using the update-manager popup on a 16.04 machine, the update process hangs:

Setting up apparmor (2.10.95-0ubuntu2.2) ...
update-rc.d: warning: start and stop actions are no longer supported; falling back to defaults
initctl: Unable to connect to Upstart: Failed to connect to socket /com/ubuntu/upstart: Connection refused
insserv: warning: script 'binfmt-support' missing LSB tags and overrides
insserv: Default-Start undefined, assuming empty start runlevel(s) for script `binfmt-support'
insserv: Default-Stop undefined, assuming empty stop runlevel(s) for script `binfmt-support'
initctl: Unable to connect to Upstart: Failed to connect to socket /com/ubuntu/upstart: Connection refused
insserv: warning: script 'screen-cleanup' missing LSB tags and overrides
insserv: Default-Start undefined, assuming empty start runlevel(s) for script `screen-cleanup'
insserv: Default-Stop undefined, assuming empty stop runlevel(s) for script `screen-cleanup'

it sits at the last line forever. this machine has no fancy os level hacks, no PPAs in use, was installed with 12.04 initially and has only seen LTS->LTS upgrades.