refactor (DMS): Replace deprecated Subquery coercion with explicit se…

…lect

src/DIRAC/DataManagementSystem/DB/test/Test_FTS3DB.py::test_raceCondition
  /Users/cburr/Development/DIRAC-dev/DIRAC/src/DIRAC/DataManagementSystem/DB/FTS3DB.py:550: SAWarning: Coercing Subquery object into a select() for use in IN(); please pass a select() construct explicitly
    .filter(~FTS3Operation.operationID.in_(opIDsWithJobAssigned))

src/DIRAC/DataManagementSystem/DB/FTS3DB.py

@@ -12,7 +12,7 @@
 from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.sql.expression import and_
 from sqlalchemy.orm import relationship, sessionmaker, mapper
-from sqlalchemy.sql import update, delete
+from sqlalchemy.sql import update, delete, select
 from sqlalchemy import (
     create_engine,
     Table,
@@ -541,7 +541,7 @@ def getNonFinishedOperations(self, limit=20, operationAssignmentTag="Assigned"):
 
             # We need to do the select in two times because the join clause that makes the limit difficult
             # We get the list of operations ID that have associated jobs assigned
-            opIDsWithJobAssigned = session.query(FTS3Job.operationID).filter(~FTS3Job.assignment.is_(None)).subquery()
+            opIDsWithJobAssigned = select(FTS3Job.operationID).filter(~FTS3Job.assignment.is_(None))
             operationIDsQuery = (
                 session.query(FTS3Operation.operationID)
                 .filter(FTS3Operation.status.in_(["Active", "Processed"]))