'Regression for ensuring ModelAdmin.fields can contain non-model fields
that broke with r11737'

def test_non_model_fields(self):

    class SongForm(forms.ModelForm, ):
        extra_data = forms.CharField()
    class FieldsOnFormOnlyAdmin(admin.ModelAdmin, ):
        form = SongForm
        fields = ['title', 'extra_data']
    FieldsOnFormOnlyAdmin.validate(Song)
