title: uninitialized constant Rails::Command::Actions::APP_PATH (NameError) when trying to start Rails engine server
body: <p>The full error is </p>
  
  <pre><code>~/.gem/ruby/2.4.0/gems/railties-5.1.5/lib/rails/command/actions.rb:8:in `set_application_directory!': uninitialized constant Rails::Command::Actions::APP_PATH (NameError)
  </code></pre>
  
  <p>I recently upgrade from Rails 4.x to 5.x.</p>