Comment 10 for bug 1204456

It is tricky in my venv environment. take "neutron.tests.unit.ml2.test_agent_scheduler.Ml2AgentSchedulerTestCase.test_network_auto_schedule_with_disabled" as an example, using $./run_tests.sh neutron.tests.unit.ml2.test_agent_scheduler.Ml2AgentSchedulerTestCase.test_network_auto_schedule_with_disabled (testr) would run okay, while using $./run_tests.sh -d neutron.tests.unit.ml2.test_agent_scheduler.Ml2AgentSchedulerTestCase.test_network_auto_schedule_with_disabled (testtools.run) would report following error:
 File "/home/stack/neutron/.venv/local/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 331, in do_execute
    cursor.execute(statement, parameters)
OperationalError: (OperationalError) no such table: ml2_vlan_allocations u'SELECT ml2_vlan_allocations.physical_network AS ml2_vlan_allocations_physical_network, ml2_vlan_allocations.vlan_id AS ml2_vlan_allocations_vlan_id, ml2_vlan_allocations.allocated AS ml2_vlan_allocations_allocated \nFROM ml2_vlan_allocations' ()