deploy: notify agents on object deletion (#7201)

hobo/deploy/signals.py

@@ -21,7 +21,7 @@ from kombu.common import Broadcast
 
 from django.conf import settings
 from django.core.signals import request_finished, request_started
-from django.db.models.signals import post_save
+from django.db.models.signals import post_save, post_delete
 from django.dispatch import receiver
 
 from .utils import get_hobo_json
@@ -37,6 +37,7 @@ tls = Local()
 
 
 @receiver(post_save)
+@receiver(post_delete)
 def post_environment_save(sender, instance, **kwargs):
     if not sender in [Variable, AttributeDefinition] + AVAILABLE_SERVICES:
         return