title: Call to undefined method Illuminate\Routing\RouteFileRegistrar::get() - Error after upgrading from Laravel 5.7 to 5.8
body: <p>I have a running app written on Laravel 5.7. I tried to change the record in <code>composer.json</code> to match "5.8.*" and ran <code>composer update</code>. On my local (win10/WAMP) machine it went fine, but on the staging server (Debian 9/nginx) the update command changed the vendor contents and failed at the end.
  Since then anything I do with the app on the server I get this error and I can't find any information anywhere.</p>
  
  <pre><code>Call to undefined method Illuminate\Routing\RouteFileRegistrar::get()
  </code></pre>
  
  <p>And this is the line that fails:</p>
  
  <pre><code>$this-&gt;get('login', 'Auth\LoginController@showLoginForm')-&gt;name('login');
  </code></pre>
  
  <p>Thanks in advance!</p>