Fix revoke for previous tasks

courses/signals.py

@@ -15,19 +15,19 @@ def lesson_created_or_updated(sender, instance: Lesson, **kwargs):
         previous_lesson = Lesson.objects.get(id=instance.id)
 
     if (not instance.id or instance.release_date != previous_lesson.release_date) and instance.release_date:
-        previous_task_hask = ''
+        previous_task_hash = ''
         ct = ContentType.objects.get_for_model(instance)
 
         st = ScheduledTask.objects.filter(content_type=ct, object_id=instance.id)
         if st.exists():
             st = st.first()
-            previous_task_hask = st.task_hash
+            previous_task_hash = st.task_hash
         else:
             st = ScheduledTask.objects.create(content_object=instance)
 
-        if previous_task_hask:
-            res = AsyncResult(previous_task_hask)
-            res.revoke()
+        if previous_task_hash:
+            from celery.task.control import revoke
+            revoke(previous_task_hash)
 
         new_task_hash = publish_lesson.apply_async(args=[instance.id], eta=instance.release_date)
         st.task_hash = new_task_hash
@@ -35,7 +35,6 @@ def lesson_created_or_updated(sender, instance: Lesson, **kwargs):
         st.release_date = instance.release_date
         st.save()
 
-
 @receiver(pre_save, sender=Unit)
 def unit_created_or_updated(sender, instance: Unit, **kwargs):
     previous_unit = Unit.objects.get(id=instance.id)