conductor

diff --git a/nova/conductor/manager.py b/nova/conductor/manager.py
index db9ab2f..cabdb00 100644
--- a/nova/conductor/manager.py
+++ b/nova/conductor/manager.py
@@ -797,11 +797,6 @@ class ComputeTaskManager(base.Base):
                 filter_properties=filter_properties,
                 legacy_bdm_in_spec=legacy_bdm)
 
-    def _get_image(self, context, image_id):
-        if not image_id:
-            return None
-        return self.image_service.show(context, image_id)
-
     def _delete_image(self, context, image_id):
         (image_service, image_id) = glance.get_remote_image_service(context,
                 image_id)
@@ -827,18 +822,27 @@ class ComputeTaskManager(base.Base):
             if snapshot_id:
                 self._delete_image(context, snapshot_id)
         elif instance.vm_state == vm_states.SHELVED_OFFLOADED:
-            try:
-                with compute_utils.EventReporter(context, self.db,
-                        'get_image_info', instance.uuid):
-                    image = self._get_image(context,
-                            sys_meta['shelved_image_id'])
-            except exception.ImageNotFound:
-                with excutils.save_and_reraise_exception():
-                    LOG.error(_('Unshelve attempted but vm_state not SHELVED '
-                                'or SHELVED_OFFLOADED'), instance=instance)
-                    instance.vm_state = vm_states.ERROR
-                    instance.save()
 
+            def raises_shelve_corrupted(instance, reason):
+                instance.vm_state = vm_states.ERROR
+                instance.save()
+                LOG.error(reason, instance)
+                raise exception.ShelvedInstanceCorrupted(
+                    instance_id=instance.uuid, reason=reason)
+
+            image_id = sys_meta.get('shelved_image_id')
+            if not image_id:
+                reason = _('Unshelve attempted but the property '
+                           'shelved_image_id cannot be found.')
+                raises_shelve_corrupted(instance, reason)
+            with compute_utils.EventReporter(
+                context, self.db, 'get_image_info', instance.uuid):
+                try:
+                    image = self.image_service.show(context, image_id)
+                except exception.ImageNotFound:
+                    reason = _('Unshelve attempted but the image %s '
+                               'cannot be found.', image_id)
+                    raises_shelve_corrupted(instance, reason)
             try:
                 with compute_utils.EventReporter(context, self.db,
                                                  'schedule_instances',