I think I remember a case or two where the zuul cloner/merger was misbehaving and using an outdated version of a repo to build the CI. This sorta reminded me to T191077 but I'm not sure this is the same case.

For some reason, rebasing those made zuul pass.

On the contint1001 zuul-merger:

2020-09-03 21:52:44,474 DEBUG zuul.Merger: Processing refspec refs/changes/77/624277/1 for project labs/libraryupgrader / master ref Zf8de0b88170946898e7ea9c925be60e8
2020-09-03 21:52:44,474 DEBUG zuul.Repo: Cloning from ssh://jenkins-bot@gerrit.wikimedia.org:29418/labs/libraryupgrader to /srv/zuul/git/labs/libraryupgrader

GitCommandError: Cmd('git') failed due to: exit code(128)

cmdline: git clone -v ssh://jenkins-bot@gerrit.wikimedia.org:29418/labs/libraryupgrader /srv/zuul/git/labs/libraryupgrader
stderr: 'fatal: destination path '/srv/zuul/git/labs/libraryupgrader' already exists and is not an empty directory.

The reason is that labs/libraryupgrader/config got created first and zuul-merger is thus unable to clone to labs/libraryupgrader since the directory already exists. The other instance on contint2001 was not affected.

I have fixed by deleting the directory and cloning labs/libraryupgrader.

That is a known issue in Zuul which happens from time to time and is listed at T157818