Fixes #4301: Fix exception when deleting device type with components

docs/release-notes/version-2.7.md

@@ -13,6 +13,7 @@
 * [#4282](https://github.com/netbox-community/netbox/issues/4282) - Fix label on export button for device types
 * [#4285](https://github.com/netbox-community/netbox/issues/4285) - Include A/Z termination sites in provider circuits table
 * [#4295](https://github.com/netbox-community/netbox/issues/4295) - Fix assignment of parent LAG during interface bulk edit
+* [#4301](https://github.com/netbox-community/netbox/issues/4301) - Fix exception when deleting device type with components
 
 ---
 

netbox/dcim/models/device_component_templates.py

@@ -1,4 +1,4 @@
-from django.core.exceptions import ValidationError
+from django.core.exceptions import ObjectDoesNotExist, ValidationError
 from django.core.validators import MaxValueValidator, MinValueValidator
 from django.db import models
 
@@ -37,11 +37,17 @@ class ComponentTemplateModel(models.Model):
         raise NotImplementedError()
 
     def to_objectchange(self, action):
+        # Annotate the parent DeviceType
+        try:
+            device_type = self.device_type
+        except ObjectDoesNotExist:
+            # The parent DeviceType has already been deleted
+            device_type = None
         return ObjectChange(
             changed_object=self,
             object_repr=str(self),
             action=action,
-            related_object=self.device_type,
+            related_object=device_type,
             object_data=serialize_object(self)
         )