First 15.6RC bug - CRA throws `Can't resolve 'create-react-class/factory'` with 15.6.0-rc.1

[flarnie]

Looks like something about the 'create-react-class' removal was not correctly cherry-picked into 15.6.

Steps to reproduce:

1. create a new CRA project
2. update the version of React in package.json to 15.6.0-rc.1
3. run yarn build

You'll get this error:

Module not found: Error: Can't resolve 'create-react-class/factory' in '/Users/flarnie/Code/react_test_projects/click_counter_two/node_modules/react/lib'