Fix code compatibility with Python 3

This code will be used when objects are registered.

Change-Id: I5399d8111fa144eb1e46623041bcc52ddee63c98
Partial-Bug: 1491258

heat/objects/resource.py

@@ -72,12 +72,9 @@ class Resource(
             return None
         for field in resource.fields:
             if field == 'data':
-                resource['data'] = map(
-                    lambda resd: resource_data.ResourceData._from_db_object(
-                        resource_data.ResourceData(context), resd
-                    ),
-                    db_resource.data
-                )
+                resource['data'] = [resource_data.ResourceData._from_db_object(
+                    resource_data.ResourceData(context), resd
+                ) for resd in db_resource.data]
             else:
                 resource[field] = db_resource[field]
 

heat/objects/service.py

@@ -48,10 +48,8 @@ class Service(base.VersionedObject,
 
     @classmethod
     def _from_db_objects(cls, context, list_obj):
-        return map(lambda obj: cls._from_db_object(context,
-                                                   cls(context),
-                                                   obj),
-                   list_obj)
+        return [cls._from_db_object(context, cls(context), obj)
+                for obj in list_obj]
 
     @classmethod
     def get_by_id(cls, context, service_id):

heat/objects/stack.py

@@ -116,23 +116,15 @@ class Stack(
     @classmethod
     def get_all(cls, context, *args, **kwargs):
         db_stacks = db_api.stack_get_all(context, *args, **kwargs)
-        stacks = map(
-            lambda db_stack: cls._from_db_object(
-                context,
-                cls(context),
-                db_stack),
-            db_stacks)
+        stacks = [cls._from_db_object(context, cls(context), db_stack)
+                  for db_stack in db_stacks]
         return stacks
 
     @classmethod
     def get_all_by_owner_id(cls, context, owner_id):
         db_stacks = db_api.stack_get_all_by_owner_id(context, owner_id)
-        stacks = map(
-            lambda db_stack: cls._from_db_object(
-                context,
-                cls(context),
-                db_stack),
-            db_stacks)
+        stacks = [cls._from_db_object(context, cls(context), db_stack)
+                  for db_stack in db_stacks]
         return stacks
 
     @classmethod