Seeing a similar failure here in a CI job run during what appears to be teardown of the test so likely the lazy load failure is due to a deleted resource:

http://logs.openstack.org/06/641806/12/check/nova-next/c7f23f4/logs/screen-c-api.txt.gz?level=TRACE#_Apr_20_23_19_28_844945

Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault [None req-eed65cf5-f6db-4782-b63f-a7191697eb5e tempest-TestEncryptedCinderVolumes-2130063619 tempest-TestEncryptedCinderVolumes-2130063619] Caught error: <class 'sqlalchemy.orm.exc.DetachedInstanceError'> Parent instance <VolumeAttachment at 0x7f570edb7320> is not bound to a Session; lazy load operation of attribute 'volume' cannot proceed (Background on this error at: http://sqlalche.me/e/bhk3): sqlalchemy.orm.exc.DetachedInstanceError: Parent instance <VolumeAttachment at 0x7f570edb7320> is not bound to a Session; lazy load operation of attribute 'volume' cannot proceed (Background on this error at: http://sqlalche.me/e/bhk3)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault Traceback (most recent call last):
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/api/middleware/fault.py", line 85, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return req.get_response(self.application)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/request.py", line 1314, in send
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     application, catch_exc_info=False)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/request.py", line 1278, in call_application
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     app_iter = application(self.environ, start_response)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 143, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return resp(environ, start_response)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 129, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     resp = self.call_func(req, *args, **kw)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 193, in call_func
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return self.func(req, *args, **kwargs)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/osprofiler/web.py", line 112, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return request.get_response(self.application)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/request.py", line 1314, in send
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     application, catch_exc_info=False)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/request.py", line 1278, in call_application
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     app_iter = application(self.environ, start_response)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 129, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     resp = self.call_func(req, *args, **kw)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 193, in call_func
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return self.func(req, *args, **kwargs)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/keystonemiddleware/auth_token/__init__.py", line 333, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     response = req.get_response(self._app)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/request.py", line 1314, in send
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     application, catch_exc_info=False)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/request.py", line 1278, in call_application
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     app_iter = application(self.environ, start_response)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 143, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return resp(environ, start_response)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 143, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return resp(environ, start_response)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/routes/middleware.py", line 141, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     response = self.app(environ, start_response)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 143, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return resp(environ, start_response)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 129, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     resp = self.call_func(req, *args, **kw)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/webob/dec.py", line 193, in call_func
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return self.func(req, *args, **kwargs)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/api/openstack/wsgi.py", line 844, in __call__
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     content_type, body, accept)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/api/openstack/wsgi.py", line 904, in _process_stack
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     action_result = self.dispatch(meth, request, action_args)
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/api/openstack/wsgi.py", line 999, in dispatch
Apr 20 23:19:28.844945 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return method(req=request, **action_args)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/api/v2/volumes.py", line 90, in detail
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return self._get_volumes(req, is_detail=True)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/api/v3/volumes.py", line 131, in _get_volumes
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     offset=offset)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/volume/api.py", line 621, in get_all
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     offset=offset)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/objects/volume.py", line 617, in get_all
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     volumes, expected_attrs=expected_attrs)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/oslo_versionedobjects/base.py", line 1133, in obj_make_list
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     **extra_args)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/objects/volume.py", line 290, in _from_db_object
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     db_volume.get('volume_attachment'))
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/oslo_versionedobjects/base.py", line 1133, in obj_make_list
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     **extra_args)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/opt/stack/new/cinder/cinder/objects/volume_attachment.py", line 102, in _from_db_object
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     if 'volume' in expected_attrs and hasattr(db_attachment, 'volume'):
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/sqlalchemy/orm/attributes.py", line 275, in __get__
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     return self.impl.get(instance_state(instance), dict_)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/sqlalchemy/orm/attributes.py", line 674, in get
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     value = self.callable_(state, passive)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault   File "/usr/local/lib/python3.6/dist-packages/sqlalchemy/orm/strategies.py", line 671, in _load_for_state
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault     % (orm_util.state_str(state), self.key)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault sqlalchemy.orm.exc.DetachedInstanceError: Parent instance <VolumeAttachment at 0x7f570edb7320> is not bound to a Session; lazy load operation of attribute 'volume' cannot proceed (Background on this error at: http://sqlalche.me/e/bhk3)
Apr 20 23:19:28.850063 ubuntu-bionic-rax-dfw-0005375337 <email address hidden>[398]: ERROR cinder.api.middleware.fault