populate_db: Use call_consume_in_tests when generating test data.

We'd rather this work be just executed immediately, rather than
queued, since queued events can confuse the queue workers if the
database is dropped and recreated repeatedly.

zilencer/management/commands/populate_db.py

@@ -478,7 +478,15 @@ def send_messages(data):
             saved_data['subject'] = message.subject
 
         message.pub_date = timezone_now()
+        # We disable USING_RABBITMQ here, so that deferred work is
+        # executed in do_send_message_messages, rather than being
+        # queued.  This is important, because otherwise, if run-dev.py
+        # wasn't running when populate_db was run, a developer can end
+        # up with queued events that reference objects from a previous
+        # life of the database, which naturally throws exceptions.
+        settings.USING_RABBITMQ = False
         do_send_messages([{'message': message}])
+        settings.USING_RABBITMQ = True
 
         recipients[num_messages] = (message_type, message.recipient.id, saved_data)
         num_messages += 1