Form provided by modelform_factory fails when using fields attribute

[Olivier Le Thanh Duong]

When creating a form using modelform_factory, setting the fields attribute and trying to display it, it fail with the following error :
AttributeError: 'NoneType' object has no attribute 'label'

Steps to reproduce :

1. run manage.py shell
   
2. import any model ex : from django.contrib.flatpages.models import FlatPage
   
3. from django.forms.models import modelform_factory
   
4. modelform_factory(FlatPage, fields='title')().as_p()
   

(or as_ul or as_table)

• > AttributeError: 'NoneType' object has no attribute 'label'

When not using this attribute or when using the excludes attribute this works as expected
Using django 1.2.3 here

[Olivier Le Thanh Duong]

A friend can reproduce this bug using 1.1.1

[Matt McClanahan]

Per ​the docs, the fields argument expects a list, not a string.

[Olivier Le Thanh Duong]

Hum this was a error of retranscription when I wrote the bug, I had actually test it with a tuple like in the doc and it didn't work either.
However when testing with a proper list it is actually working. It seems a bit strange.