Comment 2 for bug 1559300

All logic with sbuild chroot lock is here [1], and stale lock file should be removed without issues [2], but since we have some non-standard sbuild usage (in docker) it has PID 1 and as the result cannot be killed since PID 1 process is running:

/var/cache/docker-builder/sbuild/trusty-amd64/run/lock$ cat sbuild

SBUILD_UPDATE 1 root

so the only way is to remove lock file manually

rm /var/cache/docker-builder/sbuild/trusty-amd64/run/lock/sbuild

but you need to have root access

[1]. https://github.com/geofft/sbuild/blob/master/lib/Sbuild/Chroot.pm#L322
[2]. https://github.com/geofft/sbuild/blob/master/lib/Sbuild/Chroot.pm#L355

ps. the issue is fixed:
https://ci.fuel-infra.org/job/master.fuel-web.pkgs.ubuntu.review_fuel_web_deploy/702/console
and
mirrors was updated to
deb http://mirror.seed-us1.fuel-infra.org/pkgs/ubuntu/ trusty main universe multiverse restricted
deb http://mirror.seed-us1.fuel-infra.org/pkgs/ubuntu/ trusty-updates main universe multiverse restricted