feat(errors): give more context on what model is involved when 404 No…

…t Found is involved (#1096)

closes #893

rootfs/api/exceptions.py

@@ -1,3 +1,4 @@
+from django.http import Http404
 import logging
 from rest_framework.compat import set_rollback
 from rest_framework.exceptions import APIException, status
@@ -28,7 +29,12 @@ class ServiceUnavailable(APIException):
 
 
 def custom_exception_handler(exc, context):
-    # Call REST framework's default exception handler first,
+    # give more context on the error since DRF masks it as Not Found
+    if isinstance(exc, Http404):
+        set_rollback()
+        return Response(str(exc), status=status.HTTP_404_NOT_FOUND)
+
+    # Call REST framework's default exception handler after specific 404 handling,
     # to get the standard error response.
     response = exception_handler(exc, context)
 

rootfs/api/tests/test_config.py

@@ -325,3 +325,9 @@ def test_unauthorized_user_cannot_modify_config(self, mock_requests):
         body = {'values': {'FOO': 'bar'}}
         response = self.client.post(url, body)
         self.assertEqual(response.status_code, 403)
+
+    def test_config_app_not_exists(self, mock_requests):
+        url = '/v2/apps/{}/config'.format('fake')
+        response = self.client.get(url)
+        self.assertEqual(response.status_code, 404)
+        self.assertEqual(response.data, 'No App matches the given query.')