many promises: fix anomaly not returning AnomalyResult

Also add a comment when we really don't want an AnomalyResult.

See merge request !137
3 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS.Eggs.UnitTest-Master.Python3

00:17:19

failed SlapOS.Eggs.UnitTest-Master.Python3

00:17:36

failed SlapOS.Eggs.UnitTest-Master.Python3

00:34:28