@db_api.api_context_manager.writer
    def _create_api_flavor(self, context):
        fake_db_flavor = dict(fake_api_flavor)
        del fake_db_flavor['extra_specs']
        flavor = api_models.Flavors()
        flavor.update(fake_db_flavor)
        flavor.save(context.session)

        fake_db_extra_spec = {'key': 'foo', 'value': 'bar'}
        flavor_es = api_models.FlavorExtraSpecs()
        flavor_es.update(fake_db_extra_spec)
        flavor_es.save(context.session)

        return flavor

    def test_get_by_id_from_db(self):
        db_flavor = self._create_api_flavor(self.context)
        flavor = objects.Flavor.get_by_id(self.context, db_flavor['id'])
        self._compare(self, db_flavor, flavor)

Gives me:

{0} nova.tests.unit.objects.test_flavor.TestFlavor.test_get_by_flavor_id_from_db [0.020936s] ... FAILED

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):
      File "nova/tests/unit/objects/test_flavor.py", line 140, in test_get_by_flavor_id_from_db
        db_flavor = self._create_api_flavor(self.context)
      File "/home/dan/nova/.tox/py27/lib/python2.7/site-packages/oslo_db/sqlalchemy/enginefacade.py", line 709, in wrapper
        return fn(*args, **kwargs)
      File "nova/tests/unit/objects/test_flavor.py", line 120, in _create_api_flavor
        flavor.save(context.session)
      File "/home/dan/nova/.tox/py27/lib/python2.7/site-packages/oslo_db/sqlalchemy/enginefacade.py", line 781, in _property_for_context
        % (context, attr)
    oslo_db.exception.NoEngineContextEstablished: No TransactionContext is established for this <Context {'domain': None, 'project_name': None, 'project_domain': None, 'timestamp': '2016-03-17T16:54:41.744344', 'auth_token': None, 'remote_address': None, 'quota_class': None, 'resource_uuid': None, 'is_admin': False, 'user': 'fake-user', 'service_catalog': [], 'tenant': 'fake-project', 'read_only': False, 'project_id': 'fake-project', 'user_id': 'fake-user', 'show_deleted': False, 'roles': [], 'user_identity': 'fake-user fake-project - - -', 'read_deleted': 'no', 'request_id': 'req-b14950c1-384b-4450-82d1-7f889331d4ab', 'instance_lock_checked': False, 'user_domain': None, 'user_name': None}> object within the current thread; the 'session' attribute is unavailable.