code: function _checkBrowserInitializers(rootPath) {
    const isBrowserInitializersPresent = _checkInitializerTypeExists(rootPath, 'browser');
  
    if (isBrowserInitializersPresent) {
      const errorMsg = `FastBoot build no longer supports ${rootPath}/app/(instance-)?initializers/browser structure. ` +
                           `Please refer to http://ember-fastboot.com/docs/addon-author-guide#browser-only-or-node-only-initializers for a migration path.`;
      throw new Error(errorMsg);
    }
  }
docs: Helper function to check if there are any `(instance-)?intializers/browser/` path under the
  given root path and throw an error
  
  @param {String} rootPath