title: Symfony2 : Change {{ form_enctype }} to {{ form_start }} with a custom path
body: <p>I'm working on updating my code to Symfony3 standards but I come to some problems with some of my forms. I tried several things but nothing is working.</p>
  
  <p>In my twig : </p>
  
  <pre><code>&lt;form action="{{ path('paces_colle_gestioncsv_imprimer', 
  { 'id' : document.id }) }}" method="post" {{ form_enctype(form) }}&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>{{ form_enctype }} is deprecated since Symfony 2.8. I have to get the path to the controller to change it to {{ form_start }}</p>
  
  <p>In my controller : </p>
  
  <pre><code>public function ajouterErrataAction($id)
  {
      $em = $this-&gt;getDoctrine()-&gt;getManager();
  
      $document = $em-&gt;getRepository('PACESColleBundle:DocumentCSV')-&gt;find($id);
      if(!$document){
          throw $this-&gt;createNotFoundException('Document inexistant');
      }
      $colle = $document-&gt;getColle();
  
      $form = $this-&gt;createForm(ajouterErrataType::class);
  
      return $this-&gt;render('PACESColleBundle:Classement:ajouterErrata.html.twig', array(
          "colle" =&gt; $colle,
          "document" =&gt; $document,
          "form" =&gt; $form-&gt;createView()
      ));
  }
  </code></pre>
  
  <p>My formType : </p>
  
  <pre><code>public function buildForm(FormBuilderInterface $builder, array $options)
  {
      $builder
          -&gt;add('errata', TextareaType::class, array('required' =&gt; false,
                                            'attr' =&gt; array('class'=&gt;'ckeditor')
          ))
  
          -&gt;add('precision', TextareaType::class, array('required' =&gt; false,
                                               'attr' =&gt; array('class'=&gt;'ckeditor')))
  
          -&gt;add('submit',SubmitType::class, array('label' =&gt; 'Imprimer'));
      ;
  }
  </code></pre>