Reverting the .gitlab-ci.yml back to the state master was in.

1 job for 102/mike/filterDefaults in 25 seconds (queued for 3 seconds)
Name Stage Failure
whats-open-py3.7 Test
Reading package lists...
Building dependency tree...
Reading state information...
Package mysql-client is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'mysql-client' has no installation candidate
ERROR: Job failed: exit code 1