I am appending this comment to bug 1074540 because I suspect they're
related.
A recent `apt-get --auto-remove dist-upgrade` in Debian Testing hung for
me at this line in the output:
Installing new version of config file /etc/cron.d/anacron ...
`pstree` showed this:
dpkg(2935259)─┬─anacron.postins(2935268)───deb-systemd-inv(2935625)───systemctl(2935633)───systemd-tty-ask(2935634)
└─sh(2935263)───sh(2935264)───dpkg-status(2935265)
The `systemd-tty-ask` process command line was
`/usr/bin/systemd-tty-ask-password-agent --watch`. The `systemctl`
command line was `systemctl --quiet --system restart anacron.service
anacron.timer`. I tried killing the `systemd-tty-ask-password-agent`
process, but it refused to die, even with `kill -9`. I had to kill the
`systemctl --quiet --system restart anacron.service anacron.timer`
process to get the upgrade to continue.
