old_contents: import mock
  from rest_framework import test
  
  
  class MockedSession(mock.MagicMock):
      auth_ref = 'AUTH_REF'
  
  
  class BaseBackendTestCase(test.APITransactionTestCase):
      def setUp(self):
          self.session_patcher = mock.patch('keystoneauth1.session.Session', MockedSession)
          self.session_patcher.start()
  
          self.session_recover_patcher = mock.patch('nodeconductor_openstack.backend.OpenStackSession.recover')
          self.session_recover_patcher.start()
  
          self.keystone_patcher = mock.patch('keystoneclient.v2_0.client.Client')
          self.mocked_keystone = self.keystone_patcher.start()
  
          self.nova_patcher = mock.patch('novaclient.v2.client.Client')
          self.mocked_nova = self.nova_patcher.start()
  
          self.cinder_patcher = mock.patch('cinderclient.v1.client.Client')
          self.mocked_cinder = self.cinder_patcher.start()
  
      def tearDown(self):
          super(BaseBackendTestCase, self).tearDown()
          self.session_patcher.stop()
          self.keystone_patcher.stop()
          self.nova_patcher.stop()
          self.cinder_patcher.stop()
  
new_contents: import mock
  from rest_framework import test
  
  
  class MockedSession(mock.MagicMock):
      auth_ref = 'AUTH_REF'
  
  
  class BaseBackendTestCase(test.APITransactionTestCase):
      def setUp(self):
          self.session_patcher = mock.patch('keystoneauth1.session.Session', MockedSession)
          self.session_patcher.start()
  
          self.session_recover_patcher = mock.patch('nodeconductor_openstack.backend.OpenStackSession.recover')
          self.session_recover_patcher.start()
  
          self.keystone_patcher = mock.patch('keystoneclient.v2_0.client.Client')
          self.mocked_keystone = self.keystone_patcher.start()
  
          self.nova_patcher = mock.patch('novaclient.v2.client.Client')
          self.mocked_nova = self.nova_patcher.start()
  
          self.cinder_patcher = mock.patch('cinderclient.v1.client.Client')
          self.mocked_cinder = self.cinder_patcher.start()
  
      def tearDown(self):
          super(BaseBackendTestCase, self).tearDown()
          self.session_patcher.stop()
          self.session_recover_patcher.stop()
          self.keystone_patcher.stop()
          self.nova_patcher.stop()
          self.cinder_patcher.stop()
  
subject: Stop patcher in tear down