Preserve exception messages for wrapped Django exceptions (#8051)

* Preserve messages for wrapped Django exceptions

* Fix the test

* Update test_generics.py

* Update test_generics.py

Co-authored-by: Tom Christie <tom@tomchristie.com>

rest_framework/views.py

@@ -79,9 +79,9 @@ def exception_handler(exc, context):
     to be raised.
     """
     if isinstance(exc, Http404):
-        exc = exceptions.NotFound()
+        exc = exceptions.NotFound(*(exc.args))
     elif isinstance(exc, PermissionDenied):
-        exc = exceptions.PermissionDenied()
+        exc = exceptions.PermissionDenied(*(exc.args))
 
     if isinstance(exc, exceptions.APIException):
         headers = {}

tests/test_generics.py

@@ -5,6 +5,7 @@
 from django.test import TestCase
 
 from rest_framework import generics, renderers, serializers, status
+from rest_framework.exceptions import ErrorDetail
 from rest_framework.response import Response
 from rest_framework.test import APIRequestFactory
 from tests.models import (
@@ -519,7 +520,12 @@ def test_get_instance_view_filters_out_name_with_filter_backend(self):
         request = factory.get('/1')
         response = instance_view(request, pk=1).render()
         assert response.status_code == status.HTTP_404_NOT_FOUND
-        assert response.data == {'detail': 'Not found.'}
+        assert response.data == {
+            'detail': ErrorDetail(
+                string='No BasicModel matches the given query.',
+                code='not_found'
+            )
+        }
 
     def test_get_instance_view_will_return_single_object_when_filter_does_not_exclude_it(self):
         """