MA-2318: get DiscussionTopic against topic id

openedx/core/lib/exceptions.py

@@ -1,12 +1,25 @@
-""" Common Purpose Errors"""
+"""
+Common Purpose Errors
+"""
 from django.core.exceptions import ObjectDoesNotExist
 
 
 class CourseNotFoundError(ObjectDoesNotExist):
-    """ Course was not found. """
+    """
+    Course was not found.
+    """
     pass
 
 
 class PageNotFoundError(ObjectDoesNotExist):
-    """ Page was not found. Used for paginated endpoint. """
+    """
+    Page was not found. Used for paginated endpoint.
+    """
+    pass
+
+
+class DiscussionNotFoundError(ObjectDoesNotExist):
+    """
+    Discussion Module was not found.
+    """
     pass