Our production zuul would need to be attached to a second Gerrit in order to validate in production the Gerrit 3.x upgrade (T200739).
In puppet modules/zuul/templates/zuul.conf.erb we would
replace the [gerrit] section with something such as:
[connection gerrit-legacy] driver=gerrit user=jenkins-bot baseurl=https://gerrit.wikimedia.org/r sshkey=/var/lib/zuul/.ssh/id_rsa event_delay=10 [connection gerrit-new] driver=gerrit user= <XXX???XXX> baseurl= <XXX???XXX> sshkey=/var/lib/zuul/.ssh/id_rsa event_delay=10