Fix the tests and the one bug that it highlighted.

data/queue.py

@@ -1,6 +1,10 @@
 from datetime import datetime, timedelta
 
 from data.database import QueueItem, db
+from app import app
+
+
+transaction_factory = app.config['DB_TRANSACTION_FACTORY']
 
 
 class WorkQueue(object):
@@ -34,7 +38,7 @@ class WorkQueue(object):
     available_or_expired = ((QueueItem.available == True) |
                             (QueueItem.processing_expires <= now))
 
-    with db.transaction():
+    with transaction_factory(db):
       avail = QueueItem.select().where(QueueItem.queue_name == self.queue_name,
                                        QueueItem.available_after <= now,
                                        available_or_expired,