erp5_document_scanner: handle more asynchronous methods from cropper

8 jobs for for_testrunner_1 in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Master.Python2

00:21:05

passed SlapOS.Eggs.UnitTest-Master.Python3

00:19:05

passed SlapOS.Eggs.UnitTest-Master.Python2

00:26:25

passed SlapOS.Eggs.UnitTest-Master.Python2

passed SlapOS.Eggs.UnitTest-Master.Python2

00:25:41

passed SlapOS.Eggs.UnitTest-Master.Python2

00:25:39

passed SlapOS.Eggs.UnitTest-Master.Python3

00:17:28

failed SlapOS.Eggs.UnitTest-Master.Python3

00:20:38