fixing config error none

Author: silentfatez

readthedocs/rtd_tests/tests/test_doc_builder.py

@@ -159,8 +159,10 @@ def test_project_without_mkdocs_yaml(
         checkout_path.return_value = tmp_dir
         docs_dir.return_value = tmp_dir
         get_mkdocs_yaml_path.side_effect = MkDocsYAMLParseError
-        load_yaml_config.return_value = mock.Mock()
-        load_yaml_config.return_value.mkdocs = mock.Mock(configuration="mkdocs.yml")
+        mock_config = mock.Mock()
+        mock_config.mkdocs = mock.Mock(configuration="mkdocs.yml")
+
+        load_yaml_config.return_value = mock_config
         python_env = Virtualenv(
             version=self.version,
             build_env=self.build_env,