GitLab Error 502 After Update

GitLab wants to be updated on a regular basis. Most of the time, this update is painless. It happens sometimes that the update / upgrade does not work expected and the user is greeted with a
502 error:

Such an error can often be removed by reconfiguring the GitLab instance. Stop the GitLab server first

sudo gitlab-ctl stop

Perform the automatic reconfiguration:

sudo gitlab-ctl reconfigure

Start the GitLab server:

sudo gitlab-ctl start