Migrate Slapos to 3.9

See merge request !1722
9 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed Cloudooo.UnitTest-Master

01:48:22

passed SlapOS.Eggs.UnitTest-Master.Python2

00:50:22

passed SlapOS.Eggs.UnitTest-Master.Python3

00:35:57

passed SlapOS.Eggs.UnitTest-Master.Python3Next

00:30:36

failed SlapOS.KVM.ResilienceTest-Master

00:50:43

passed SlapOS.SoftwareReleases.IntegrationTest-Master

09:32:51

passed SlapOS.Theia.ResilienceTest-Master-ERP5

06:50:31

passed SlapOS.Theia.ResilienceTest-Master-Gitlab

12:50:09

failed Zodbtools.UnitTest-Master.ZODB6.Python3

00:00:48