Resolve TMSS-666

Closes TMSS-666 There is a followup ticket TMSS-729 to kill the pipeline.

SAS/TMSS/backend/test/t_scheduling.py

@@ -75,6 +75,7 @@ from lofar.sas.resourceassignment.resourceassigner.rarpc import RARPC
 from lofar.sas.tmss.tmss.tmssapp import models
 from lofar.sas.tmss.tmss.tmssapp.subtasks import *
 from lofar.sas.tmss.tmss.tmssapp.tasks import *
+from lofar.sas.tmss.test.test_utils import set_subtask_state_following_allowed_transitions
 from lofar.messaging.rpc import RPCService, ServiceMessageHandler
 import threading