Fixed SchemaView to reset renderer on exception. (#6429)

Fixes #6258.

rest_framework/schemas/views.py

@@ -31,3 +31,11 @@ class SchemaView(APIView):
         if schema is None:
             raise exceptions.PermissionDenied()
         return Response(schema)
+
+    def handle_exception(self, exc):
+        # Schema renderers do not render exceptions, so re-perform content
+        # negotiation with default renderers.
+        self.renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES
+        neg = self.perform_content_negotiation(self.request, force=True)
+        self.request.accepted_renderer, self.request.accepted_media_type = neg
+        return super(SchemaView, self).handle_exception(exc)

tests/test_schemas.py

@@ -1304,3 +1304,13 @@ class TestAutoSchemaAllowsFilters(object):
 
     def test_FOO(self):
         assert not self._test('FOO')
+
+
+@pytest.mark.skipif(not coreapi, reason='coreapi is not installed')
+def test_schema_handles_exception():
+    schema_view = get_schema_view(permission_classes=[DenyAllUsingPermissionDenied])
+    request = factory.get('/')
+    response = schema_view(request)
+    response.render()
+    assert response.status_code == 403
+    assert "You do not have permission to perform this action." in str(response.content)