Merge pull request #3498 from raymond-devries/3445-traceback-for-none

View returned none exception contains endpoint name

src/flask/app.py

@@ -2078,9 +2078,9 @@ class Flask(_PackageBoundObject):
         # the body must not be None
         if rv is None:
             raise TypeError(
-                "The view function did not return a valid response. The"
+                'The view function for "{}" did not return a valid response. The'
                 " function either returned None or ended without a return"
-                " statement."
+                " statement.".format(request.endpoint)
             )
 
         # make sure the body is an instance of the response class

tests/test_basic.py

@@ -1221,6 +1221,7 @@ def test_response_type_errors():
     with pytest.raises(TypeError) as e:
         c.get("/none")
         assert "returned None" in str(e.value)
+        assert "from_none" in str(e.value)
 
     with pytest.raises(TypeError) as e:
         c.get("/small_tuple")