title: Why do I get an object is not iterable error?
body: <p>Why do I get the following error in my app</p>
  
  <pre><code>Caught TypeError while rendering: 'ModelNameHere' object is not iterable
  </code></pre>
  
  <p>but I don't get it when I execute it from the shell?</p>
  
  <p>I just have a custom field in my form which inherits from forms.ModelForm</p>
  
  <pre><code>custom_serving_size = forms.ChoiceField(
      ServingSize.objects.all(),
      widget=forms.Select(attrs={'class':'ddl'})
  )
  </code></pre>
  
  <p><strong>EDIT</strong></p>
  
  <p>This is my form class</p>
  
  <pre><code>class RecipeIngredientForm(forms.ModelForm):
      serving_size = forms.ChoiceField(choices=ServingSize.objects.all())
  </code></pre>
  
  <p>The error happens on ServingSize.objects.all()</p>