CORD-1345: Rename PlCoreBase to XOSBase

Change-Id: Ide26de9abc0cc6d0a9c5c92362b9717ad51af105
diff --git a/xos/attic/header.py b/xos/attic/header.py
index deadcaf..33498dd 100644
--- a/xos/attic/header.py
+++ b/xos/attic/header.py
@@ -1,6 +1,6 @@
 from django.db import models
-from core.models import Service, PlCoreBase, Slice, Instance, Tenant, TenantWithContainer, Node, Image, User, Flavor
-from core.models.plcorebase import StrippedCharField
+from core.models import Service, XOSBase, Slice, Instance, Tenant, TenantWithContainer, Node, Image, User, Flavor
+from core.models.xosbase import StrippedCharField
 import os
 from django.db import models, transaction
 from django.forms.models import model_to_dict