Comment 4 for bug 1958389

I've tested manually on a staging lcy02 builder and it works fine there, so worst case you should be able to retry until it happens to land on lcy02.

I've reproduced the problem on a staging lgw01 builder. I need ddebs to get a useful backtrace, so I've filed https://code.launchpad.net/~cjwatson/canonical-is-firewalls/+git/firewall-configs/+merge/414372 to get access to those from the relevant builder - I should be able to pick this up again once that's merged.