React.__spread is deprecated and should not be used

[johdah]

I get this with React 15.1.0

react-with-addons.js:21693 Warning: React.__spread is deprecated and should not be used. Use Object.assign directly or another helper function with similar semantics. You may be seeing this warning due to your compiler. See https://fb.me/react-spread-deprecation for more details.

A facebook member wrote the following in the React project (facebook/react#6444):

If you are using react-tools to compile JSX, please switch to Babel. That project was unsupported for more than a year.