[slapos.core] improve format

See merge request !365
7 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS-Master.UnitTest-Master

01:41:38

failed SlapOS.Eggs.UnitTest-Master.Python2

00:22:37

failed SlapOS.Eggs.UnitTest-Master.Python3

00:23:23

passed SlapOS-Master.UnitTest-Master

01:47:27

passed SlapOS-Master.UnitTest-Master

failed SlapOS.Eggs.UnitTest-Master.Python2

00:12:06

failed SlapOS.Eggs.UnitTest-Master.Python3

00:27:26