Ensure errors_out_migration errors out migration

errors_out_migration_ctxt includes a check of the current migration
state.  If the migration is not in either 'migrating' or
'post-migrating', the decorator will not set it to an error state.
This behaviour has been present since the decorator was added in
change Ie752e483. The change does not describe why this restriction is
present and there is no comment, so we can only guess why it exists.

My best guess is that it is a hack to limit the scope of the
decorator. The idea might have been that if the migration status has
been set to some value representing that is has finished or moved to
another host, we should no longer set the migration to an error state
if there is a subsequent error which wouldn't directly affect the
instance.

With changes Id2f352a6 and I9bcc1605 we have removed the necessity for
this by defining the scope in which we should set a migration to error
to the lexical scope of the context manager. We remove this exclusion
as its implementation is obtuse, we have replaced its functionality,
and it makes extending migration code harder.

Change-Id: Ib6156d8e2500cee441c6c04fbe91b5c8eff488b0

nova/compute/manager.py

@@ -114,16 +114,8 @@ def errors_out_migration_ctxt(migration):
 
     try:
         yield
-    except Exception as ex:
+    except Exception:
         with excutils.save_and_reraise_exception():
-            # NOTE(rajesht): If InstanceNotFound error is thrown from
-            # decorated function, migration status should be set to
-            # 'error', without checking current migration status.
-            if not isinstance(ex, exception.InstanceNotFound):
-                status = migration.status
-                if status not in ['migrating', 'post-migrating']:
-                    return
-
             migration.status = 'error'
             try:
                 with migration.obj_as_admin():

nova/tests/unit/compute/test_compute_mgr.py

@@ -19,7 +19,6 @@ import time
 
 from cinderclient import exceptions as cinder_exception
 from cursive import exception as cursive_exception
-import ddt
 from eventlet import event as eventlet_event
 import mock
 import netaddr
@@ -5385,7 +5384,6 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
             self.assertEqual(expected_call, create_error_call)
 
 
-@ddt.ddt
 class ComputeManagerErrorsOutMigrationTestCase(test.NoDBTestCase):
     def setUp(self):
         super(ComputeManagerErrorsOutMigrationTestCase, self).setUp()
@@ -5436,21 +5434,6 @@ class ComputeManagerErrorsOutMigrationTestCase(test.NoDBTestCase):
         mock_save.assert_called_once_with()
         mock_obj_as_admin.assert_called_once_with()
 
-    @ddt.data('completed', 'finished')
-    @mock.patch.object(objects.Migration, 'save')
-    def test_status_exclusion(self, status, mock_save):
-        # Tests that errors_out_migration doesn't error out migration if the
-        # status is anything other than 'migrating' or 'post-migrating'
-        self.migration.status = status
-
-        def test_function():
-            with manager.errors_out_migration_ctxt(self.migration):
-                raise test.TestingException()
-
-        self.assertRaises(test.TestingException, test_function)
-        self.assertEqual(status, self.migration.status)
-        mock_save.assert_not_called()
-
 
 class ComputeManagerMigrationTestCase(test.NoDBTestCase):
     class TestResizeError(Exception):