flask-restful test failure

gistfile1.txt

_________________ APITestCase.test_exception_header_forwarded __________________

self = <tests.test_api.APITestCase testMethod=test_exception_header_forwarded>

    def test_exception_header_forwarded(self):
        """Test that HTTPException's headers are extended properly"""
        app = Flask(__name__)
        app.config['DEBUG'] = True
        api = flask_restful.Api(app)

        class NotModified(HTTPException):
            code = 304

            def __init__(self, etag, *args, **kwargs):
                super(NotModified, self).__init__(*args, **kwargs)
                self.etag = quote_etag(etag)

            def get_headers(self, *args, **kwargs):
                """Get a list of headers."""
                return [('ETag', self.etag)]

        class Foo1(flask_restful.Resource):
            def get(self):
                flask_abort(304, etag='myETag')

        api.add_resource(Foo1, '/foo')
        _aborter.mapping.update({304: NotModified})

        with app.test_client() as client:
>           foo = client.get('/foo')

tests/test_api.py:817:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
/nix/store/n4rlpm3bf4y51vdcqxsr0hjxv2pmkdas-python3.9-werkzeug-2.2.2/lib/python3.9/site-packages/werkzeug/test.py:1140: in get
    return self.open(*args, **kw)
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/testing.py:223: in open
    response = super().open(
/nix/store/n4rlpm3bf4y51vdcqxsr0hjxv2pmkdas-python3.9-werkzeug-2.2.2/lib/python3.9/site-packages/werkzeug/test.py:1094: in open
    response = self.run_wsgi_app(request.environ, buffered=buffered)
/nix/store/n4rlpm3bf4y51vdcqxsr0hjxv2pmkdas-python3.9-werkzeug-2.2.2/lib/python3.9/site-packages/werkzeug/test.py:961: in run_wsgi_app
    rv = run_wsgi_app(self.application, environ, buffered=buffered)
/nix/store/n4rlpm3bf4y51vdcqxsr0hjxv2pmkdas-python3.9-werkzeug-2.2.2/lib/python3.9/site-packages/werkzeug/test.py:1242: in run_wsgi_app
    app_rv = app(environ, start_response)
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/app.py:2548: in __call__
    return self.wsgi_app(environ, start_response)
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/app.py:2528: in wsgi_app
    response = self.handle_exception(e)
flask_restful/__init__.py:271: in error_router
    return original_handler(e)
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/app.py:2525: in wsgi_app
    response = self.full_dispatch_request()
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/app.py:1822: in full_dispatch_request
    rv = self.handle_user_exception(e)
flask_restful/__init__.py:271: in error_router
    return original_handler(e)
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/app.py:1820: in full_dispatch_request
    rv = self.dispatch_request()
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/app.py:1796: in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
flask_restful/__init__.py:467: in wrapper
    resp = resource(*args, **kwargs)
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/views.py:107: in view
    return current_app.ensure_sync(self.dispatch_request)(**kwargs)
flask_restful/__init__.py:582: in dispatch_request
    resp = meth(*args, **kwargs)
tests/test_api.py:811: in get
    flask_abort(304, etag='myETag')
/nix/store/mizjj4ilcgzrbz0nq96nzr9gwk4yiicd-python3.9-flask-2.2.2/lib/python3.9/site-packages/flask/helpers.py:310: in abort
    current_app.aborter(code, *args, **kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <werkzeug.exceptions.Aborter object at 0x7ffff5679cd0>, code = 304
args = (), kwargs = {'etag': 'myETag'}
Response = <class 'werkzeug.sansio.response.Response'>

    def __call__(
        self, code: t.Union[int, "Response"], *args: t.Any, **kwargs: t.Any
    ) -> "te.NoReturn":
        from .sansio.response import Response

        if isinstance(code, Response):
            raise HTTPException(response=code)

        if code not in self.mapping:
>           raise LookupError(f"no exception for {code!r}")
E           LookupError: no exception for 304

/nix/store/n4rlpm3bf4y51vdcqxsr0hjxv2pmkdas-python3.9-werkzeug-2.2.2/lib/python3.9/site-packages/werkzeug/exceptions.py:862: LookupError