format: fix callAndRead for python3

See merge request !399
4 jobs for master in 0 seconds (queued for 1 second)
Status Job ID Name Coverage
  External
failed SlapOS-Master.UnitTest-Master

01:48:45

passed SlapOS.Eggs.UnitTest-Master.Python2

00:12:13

passed SlapOS.Eggs.UnitTest-Master.Python3

00:16:44

passed SlapOS.Eggs.UnitTest-Master.Python2

00:14:13