python: cannot concatenate 'str' and 'long' objects

I'm trying to set up a choice field in django, but I don't think this is a django issue. The choices field takes an iterable (e.g., a list or tuple) of 2-tuples to use as choices for this field.

Here's my code:

self.fields['question_' + question.id] = forms.ChoiceField(
                label=question.label,
                help_text=question.description,
                required=question.answer_set.required,
                choices=[("fe", "a feat"), ("faaa", "sfwerwer")])

for some reason, i always get the following error:

TypeError - cannot concatenate 'str' and 'long' objects

The last line is always highlighted.

I'm not trying to concatenate anything. Almost regardless of what I change the list to for the 'choices' parameter, I get this error.

What's going on?