Replaced another console.error() call with fbjs warning()

Author: Brian Vaughn

addons/react-addons-test-utils/index.js

@@ -9,10 +9,13 @@
 
 'use strict';
 
+var warning = require('fbjs/lib/warning');
+
 // This package has been deprecated in NPM as of version 15.5.0
 // But NPM deprecation warnings are easy to overlook
 // So a more explicit runtime warning seemed appropriate
-console.error(
+warning(
+  false,
   'ReactTestUtils has been moved to react-dom/test-utils. ' +
   'Update references to remove this warning.'
 );

addons/react-addons-test-utils/test.js

@@ -24,7 +24,7 @@ describe('ReactTestUtils', function() {
 
   it('should warn on include', function() {
     expect(console.error).toHaveBeenCalledWith(
-      'ReactTestUtils has been moved to react-dom/test-utils. ' +
+      'Warning: ReactTestUtils has been moved to react-dom/test-utils. ' +
       'Update references to remove this warning.'
     );
   });