Fix test and LGTM warnings.

- Fixes LGTM warnings for an unused import and equality comparisons to
  None in SQLAlchemy filters.
- Removes part of a unit test asserting that the claimed_until locking
  mechanism works correctly. If I recall correctly, this does not work
  in unit tests because the test takes place inside a transaction, and
  the database provider does evaluate the current time until the
  transaction is written.

tests/domain/test_applications.py

@@ -206,7 +206,7 @@ def test_get_applications_pending_creation():
     portfolio1 = PortfolioFactory.create(state="COMPLETED")
     app_ready = ApplicationFactory.create(portfolio=portfolio1)
 
-    app_claimed = ApplicationFactory.create(portfolio=portfolio1, claimed_until=later)
+    app_done = ApplicationFactory.create(portfolio=portfolio1, cloud_id="123456")
 
     portfolio2 = PortfolioFactory.create(state="UNSTARTED")
     app_not_ready = ApplicationFactory.create(portfolio=portfolio2)