Packages missing for credentials-3

[Michi Henning]

When configuring newly added slaves, I recently got this:

02:31:11 Started by upstream project "credentials-3-launchpad-plugin"
build number 17
02:31:11 originally caused by:
02:31:11 Started by user Michi Henning
02:31:11 Building remotely on jenkins-slave-15 (launchpad armhf) in
workspace
/var/lib/jenkins/slaves/jenkins-slave-15/workspace/credentials-3-launchpad-plugin/node/jenkins-slave-15
02:31:11 [jenkins-slave-15] $ /bin/bash /tmp/hudson3144458127330095771.sh
02:31:11 Reading package lists...
02:31:11 Building dependency tree...
02:31:11 Reading state information...
02:31:11 E: Unable to locate package tarmac
02:31:11 E: Unable to locate package jenkins-launchpad-plugin
02:31:12 Build step 'Execute shell' marked build as failure
02:31:12 Finished: FAILURE

Looks like we need to add the relevant repositories as part of the job.