objects: add HyperVLiveMigrateData stub

This class seems to have been considered a base class, supposed
to be inherited by driver specific implementation, not being
registered within the versioned object registry.

Hyper-V does not use this object, so it does not have a driver
specific implementation. During live migration, a LiveMigrateData
object will be passed via RPC, which will fail as it can't be
deserialized.

As a result, this issue breaks Hyper-V live migration.

This patch adds the HyperVLiveMigrateData object in order to avoid
this issue.

Change-Id: I0bd1c21334a2a21afadb6608edca1f81987b32d4
Closes-bug: #1550391

nova/objects/migrate_data.py

@@ -252,3 +252,8 @@ class XenapiLiveMigrateData(LiveMigrateData):
         if 'pre_live_migration_result' in legacy:
             self.sr_uuid_map = \
                 legacy['pre_live_migration_result']['sr_uuid_map']
+
+
+@obj_base.NovaObjectRegistry.register
+class HyperVLiveMigrateData(LiveMigrateData):
+    VERSION = '1.0'

nova/tests/unit/objects/test_objects.py

@@ -1122,6 +1122,7 @@ object_data = {
     'FloatingIP': '1.10-52a67d52d85eb8b3f324a5b7935a335b',
     'FloatingIPList': '1.11-7f2ba670714e1b7bab462ab3290f7159',
     'HostMapping': '1.0-1a3390a696792a552ab7bd31a77ba9ac',
+    'HyperVLiveMigrateData': '1.0-0b868dd6228a09c3f3e47016dddf6a1c',
     'HVSpec': '1.2-db672e73304da86139086d003f3977e7',
     'ImageMeta': '1.8-642d1b2eb3e880a367f37d72dd76162d',
     'ImageMetaProps': '1.12-6a132dee47931447bf86c03c7006d96c',

nova/virt/hyperv/livemigrationops.py

@@ -93,7 +93,7 @@ class LiveMigrationOps(object):
                                            block_migration=False,
                                            disk_over_commit=False):
         LOG.debug("check_can_live_migrate_destination called", instance_ref)
-        return migrate_data_obj.LiveMigrateData()
+        return migrate_data_obj.HyperVLiveMigrateData()
 
     def check_can_live_migrate_destination_cleanup(self, ctxt,
                                                    dest_check_data):