promise/plugin: improve check-rx-saturated messages

6 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS.Eggs.UnitTest-Master.Python3

00:18:23

failed SlapOS.Eggs.UnitTest-Master.Python3

00:16:45

failed SlapOS.Eggs.UnitTest-Master.Python3

00:17:08

failed SlapOS.Eggs.UnitTest-Master.Python3

00:18:12

failed SlapOS.Eggs.UnitTest-Master.Python3

00:18:01

failed SlapOS.Eggs.UnitTest-Master.Python3

00:19:25