from django import forms
from django.conf import settings
from django.contrib.flatpages.models import FlatPage
from django.utils.translation import ugettext, ugettext_lazy as _

class FlatpageForm(forms.ModelForm):
    url = forms.RegexField(label=_("URL"), max_length=100, regex=r'^[-\w/\.~]+$',
        help_text = _("Example: '/about/contact/'. Make sure to have leading"
                      " and trailing slashes."),
        error_message = _("This value must contain only letters, numbers,"
                          " dots, underscores, dashes, slashes or tildes."))

    class Meta:
        model = FlatPage

    def clean_url(self):
        url = self.cleaned_data['url']
        if not url.startswith('/'):
            raise forms.ValidationError(ugettext("URL is missing a leading slash."))
        if (settings.APPEND_SLASH and
            'django.middleware.common.CommonMiddleware' in settings.MIDDLEWARE_CLASSES and
            not url.endswith('/')):
            raise forms.ValidationError(ugettext("URL is missing a trailing slash."))
        return url

    def clean(self):
        url = self.cleaned_data.get('url', None)
        sites = self.cleaned_data.get('sites', None)

        same_url = FlatPage.objects.filter(url=url)
        if self.instance.pk:
            same_url = same_url.exclude(pk=self.instance.pk)

        if sites and same_url.filter(sites__in=sites).exists():
            for site in sites:
                if same_url.filter(sites=site).exists():
                    raise forms.ValidationError(
                        _('Flatpage with url %(url)s already exists for site %(site)s' %
                          {'url': url, 'site': site}))

        return super(FlatpageForm, self).clean()

@@ -1622,16 +1622,17 @@
 (site)s'
+)
  %25%0A     
@@ -1679,17 +1679,16 @@
 : site%7D)
-)
 %0A%0A      

Update django/contrib/flatpages/forms.py