callable readonly_fields on inline admins have stopped working in trunk

[jbg@…]

Attempting to list a callable (either from the model or the inline admin object) in readonly_fields does nothing (no error, but it doesn't appear either). Additionally listing it in 'fields' leads to the following exception:

  File "/home/.../django/django/contrib/admin/options.py", line 1391, in changeform_view
    formsets, inline_instances = self._create_formsets(request, obj)
  File "/home/.../django/django/contrib/admin/options.py", line 1685, in _create_formsets
    for FormSet, inline in self.get_formsets_with_inlines(*get_formsets_args):
  File "/home/.../django/django/contrib/admin/options.py", line 736, in get_formsets_with_inlines
    yield inline.get_formset(request, obj), inline
  File "/home/.../django/django/contrib/admin/options.py", line 1832, in get_formset
    return inlineformset_factory(self.parent_model, self.model, **defaults)
  File "/home/.../django/django/forms/models.py", line 1013, in inlineformset_factory
    FormSet = modelformset_factory(model, **kwargs)
  File "/home/.../django/django/forms/models.py", line 835, in modelformset_factory
    labels=labels, help_texts=help_texts, error_messages=error_messages)
  File "/home/.../django/django/forms/models.py", line 545, in modelform_factory
    return type(form)(class_name, (form,), form_class_attrs)
  File "/home/.../django/django/forms/models.py", line 293, in __new__
    raise FieldError(message)
django.core.exceptions.FieldError: Unknown field(s) (name_of_field) specified for NameOfModel

[Tim Graham]

I couldn't reproduce this using the information you provided. Could you include minimal sample code to reproduce and bisect to the commit where the behavior changed?