fup: Print message logging uncaught nova-manage exceptions

While these commands would previously use LOG.exception to at least log
the exceptions in nova-manage.log the user wouldn't see anything printed
to stdout by default. This change logs a simple message to the user
pointing them in the direction of the more verbose log if they need
more help.

Conflicts:
     nova/cmd/manage.py
     nova/tests/unit/cmd/test_manage.py

NOTE(auniyal):
     changes for class VolumeAttachmentCommands are not required to
     backport as class does not exists in stable/wallaby

Change-Id: I28ed8e35e057e5b57d1da437616f8aff1a184fe4
(cherry picked from commit bbcd7d2)

Author: lyarwood

nova/cmd/manage.py

@@ -2662,7 +2662,9 @@ def get_machine_type(self, instance_uuid=None):
                 exception.InstanceMappingNotFound) as e:
             print(str(e))
             return 2
-        except Exception:
+        except Exception as e:
+            print('Unexpected error, see nova-manage.log for the full '
+                  'trace: %s ' % str(e))
             LOG.exception('Unexpected error')
             return 1
 
@@ -2716,7 +2718,9 @@ def update_machine_type(
         ) as e:
             print(str(e))
             return 2
-        except Exception:
+        except Exception as e:
+            print('Unexpected error, see nova-manage.log for the full '
+                  'trace: %s ' % str(e))
             LOG.exception('Unexpected error')
             return 1
 
@@ -2747,7 +2751,9 @@ def list_unset_machine_type(self, cell_uuid=None):
         except exception.CellMappingNotFound as e:
             print(str(e))
             return 2
-        except Exception:
+        except Exception as e:
+            print('Unexpected error, see nova-manage.log for the full '
+                  'trace: %s ' % str(e))
             LOG.exception('Unexpected error')
             return 1
 

nova/tests/unit/cmd/test_manage.py

@@ -3050,10 +3050,14 @@ def test_get(self, mock_get_context, mock_get_machine_type):
     def test_get_unknown_failure(
         self, mock_get_context, mock_get_machine_type
     ):
-        mock_get_machine_type.side_effect = Exception()
+        mock_get_machine_type.side_effect = Exception('oops')
         ret = self.commands.get_machine_type(
             instance_uuid=uuidsentinel.instance
         )
+        output = self.output.getvalue().strip()
+        self.assertIn(
+            'Unexpected error, see nova-manage.log for the full trace: oops',
+            output)
         self.assertEqual(1, ret)
 
     @mock.patch('nova.virt.libvirt.machine_type_utils.get_machine_type')
@@ -3145,11 +3149,15 @@ def test_update_force(self, mock_get_context, mock_update):
     @mock.patch('nova.virt.libvirt.machine_type_utils.update_machine_type')
     @mock.patch('nova.context.get_admin_context', new=mock.Mock())
     def test_update_unknown_failure(self, mock_update):
-        mock_update.side_effect = Exception()
+        mock_update.side_effect = Exception('oops')
         ret = self.commands.update_machine_type(
             instance_uuid=uuidsentinel.instance,
             machine_type=mock.sentinel.machine_type
         )
+        output = self.output.getvalue().strip()
+        self.assertIn(
+            'Unexpected error, see nova-manage.log for the full trace: oops',
+            output)
         self.assertEqual(1, ret)
 
     @mock.patch('nova.virt.libvirt.machine_type_utils.update_machine_type')
@@ -3269,9 +3277,13 @@ def test_list_unset_machine_type_none_found(
     def test_list_unset_machine_type_unknown_failure(
         self, mock_get_context, mock_get_instances
     ):
-        mock_get_instances.side_effect = Exception()
+        mock_get_instances.side_effect = Exception('oops')
         ret = self.commands.list_unset_machine_type(
             cell_uuid=uuidsentinel.cell_uuid)
+        output = self.output.getvalue().strip()
+        self.assertIn(
+            'Unexpected error, see nova-manage.log for the full trace: oops',
+            output)
         self.assertEqual(1, ret)
 
     @mock.patch(