title: The "X" argument does not exist
body: <p>I have a simple symfony console application with following entry point</p>
  
  <pre><code>#!/usr/bin/env php
  &lt;?php
  
  include __DIR__ . '/vendor/autoload.php';
  
  use Rkmax\Application;
  
  $app = new Application();
  $app-&gt;run();
  </code></pre>
  
  <p>my Application class</p>
  
  <pre><code>class Application extends BaseApplication
  {
      public function __construct($name = 'myapp', $version = '0.1')
      {
          parent::__construct($name, $version);
  
          $this-&gt;add(new Command\SingleCommand());
      }
  }
  </code></pre>
  
  <p>and my command</p>
  
  <pre><code>class SingleCommand extends Command
  {
      const KEYWORDS = 'keywords';
  
      protected function configure()
      {
          $this
              -&gt;setName("single")
              -&gt;setDescription("Sample")
              -&gt;addArgument(self::KEYWORDS, InputArgument::OPTIONAL, "Keywords for the search")
          ;
      }
  
      public function run(InputInterface $input, OutputInterface $output)
      {
          $keywords = $input-&gt;getArgument(self::KEYWORDS);
          // ...
      }
  }
  </code></pre>
  
  <p>i cant understand where is the problem always i get the error</p>
  
  <pre><code> [InvalidArgumentException]               
   The "keywords" argument does not exist.
  </code></pre>