title: Failed deploying rails app with webpacker to heroku
body: <h1>Environment</h1>
  
  <ul>
  <li>Rails 5.1.5</li>
  <li>webpack 3.11.0</li>
  </ul>
  
  <h1>Error message</h1>
  
  <pre><code>remote:        Webpacker is installed  
  remote:        Using /tmp/build_a60546bb726d2fa7f4b8b4ac052f461e/config/webpacker.yml file for setting up webpack paths
  remote:        Compiling…
  remote:        Compilation failed:
  remote:        bundler: failed to load command: webpack (/tmp/build_a60546bb726d2fa7f4b8b4ac052f461e/vendor/bundle/ruby/2.3.0/bin/webpack)
  remote:        Errno::ENOENT: No such file or directory - /tmp/build_a60546bb726d2fa7f4b8b4ac052f461e/node_modules/.bin/webpack
  </code></pre>