我总是装完yarn。
=> Booting Puma
=> Rails 6.0.0.rc2 application starting in development
=> Run `rails server --help` for more startup options
Usage: yarn [options]
yarn: error: no such option: --integrity
========================================
Your Yarn packages are out of date!
Please run `yarn install --check-files` to update.
========================================
To disable this check, please change `check_yarn_integrity`
to `false` in your webpacker config file (config/webpacker.yml).