def test_forbiddenResource(self):
        """
        If the file in the filesystem which would satisfy a request cannot be
        read, L{File.render} sets the HTTP response code to I{FORBIDDEN}.
        """
        base = FilePath(self.mktemp())
        base.setContent(b'')
        # Make sure we can delete the file later.
        self.addCleanup(base.chmod, 0o700)

        # Get rid of our own read permission.
        base.chmod(0)

        file = static.File(base.path)
        request = DummyRequest([b''])
        d = self._render(file, request)
        def cbRendered(ignored):
            self.assertEqual(request.responseCode, 403)
        d.addCallback(cbRendered)
        return d

        If the file in the filesystem which would satisfy a request cannot be
        read, L{File.render} sets the HTTP response code to I{FORBIDDEN}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_static.py