title: Laravel whoops and class str not found
body: <p>I have tried to update my Laravel from 5.4 to 5.5 but I am having some errors-</p>
  
  <blockquote>
    <p>Uncaught Error: Call to undefined method
    Whoops\Handler\PrettyPageHandler::setApplicationPaths() in...</p>
  </blockquote>
  
  <p>Laravel log shows something like this-</p>
  
  <blockquote>
    <p>production.ERROR: Class 'str' not found {"exception":"[object]
    (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0):
    Class 'str' not found at
    C:\xampp\htdocs\teste\config\cache.php:91) [stacktrace]</p>
    
    <p>production.ERROR: Class 'str' not found {"exception":"[object]
    (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0):
    Class 'str' not found at
    C:\xampp\htdocs\teste\config\cache.php:91) [stacktrace]</p>
  </blockquote>
  
  <p>This is how my cache.php looks-</p>
  
  <pre><code>'prefix' =&gt; env(
      'CACHE_PREFIX',
      str::slug(env('APP_NAME', 'laravel'), '_').'_cache'
   ),
  </code></pre>
  
  <p>The line 91 is the str::slug. Any idea what am I missing?</p>