not work with CKEDITOR (django-ckeditor)

[matinfo]

When I try to use Ckeditor field widget, like this:

from django import forms
from django.contrib import admin
from django.utils.translation import ugettext_lazy as _
from django.conf import settings

from flatpages_i18n.models import FlatPage_i18n
from flatpages_i18n.admin import FlatPageAdmin as BaseFlatPageAdmin
from flatpages_i18n.forms import FlatpageForm as BaseFlatpageForm

from ckeditor.widgets import CKEditorWidget

class FlatpageForm(BaseFlatpageForm):

    for lang in settings.LANGUAGES:
        field_id = 'content_%s' % lang[0]
        locals()[field_id] = forms.CharField(widget=CKEditorWidget(), \
            required=False, label=_(u'Content %s' % lang[0]))

    class Meta:
        model = FlatPage_i18n

class FlatPageAdmin(BaseFlatPageAdmin): 
    form = FlatpageForm


admin.site.unregister(FlatPage_i18n)
admin.site.register(FlatPage_i18n, FlatPageAdmin)

The editor is correctly display on the admin view, but when you try to save the form, this fail and return the error "Please correct the error below", but not field of the form is highlighted with an error.