title: Hidden field in Django form not in cleaned_data
body: <p>I have this form:</p>
  
  <pre><code>class CollaboratorForm(forms.Form):
      user = forms.CharField(label="Username",max_length=100)
      canvas = forms.IntegerField(widget=forms.HiddenInput)
      ....
      def clean_user(self):
          user = self.cleaned_data['user']
          canvas = self.cleaned_data['canvas']
  </code></pre>
  
  <p>In the view I'm simply calling</p>
  
  <pre><code>if form.is_valid():
  </code></pre>
  
  <p>I get the error:</p>
  
  <pre><code>KeyError at /canvas/1/add-collaborator/
  'canvas'
  </code></pre>
  
  <p>According to firebug the value is posting, it's just doesn't seem to be making it to my clean function. Am I doing it wrong?</p>
  
  <p>EDIT: Post data</p>
  
  <pre><code>canvas  1
  csrfmiddlewaretoken 2cb73be791b32ca9a41566082c804312
  user    username
  </code></pre>
  
  <p>EDIT2: I would also be willing to take an answer that could tell me how to send the primary key to the clean_user function, where the primary key is the /1/ in the example url above. The function in the view that is called is:</p>
  
  <pre><code>def canvas_add_collaborator(request, pk):
  </code></pre>
  
  <p>So I would want to send the pk to the clean_user function which would solve my problem by not needing the hidden field.</p>