Fixed #17057 -- Corrected flatpage url uniqueness validation to account for flatpage editing.

        url = self.cleaned_data.get('url', None)

        sites = self.cleaned_data.get('sites', None)

        flatpages_with_same_url = FlatPage.objects.filter(url=url)

        same_url = FlatPage.objects.filter(url=url)

        if self.instance.pk:

            same_url = same_url.exclude(pk=self.instance.pk)

        if flatpages_with_same_url.filter(sites__in=sites).exists():

        if same_url.filter(sites__in=sites).exists():

            for site in sites:

                if flatpages_with_same_url.filter(sites=site).exists():

                if same_url.filter(sites=site).exists():

                    raise forms.ValidationError(

                        _('Flatpage with url %s already exists for site %s'

                          % (url, site)))

from django.conf import settings

from django.contrib.flatpages.forms import FlatpageForm

from django.contrib.flatpages.models import FlatPage

from django.test import TestCase

class FlatpageAdminFormTests(TestCase):

        self.assertEqual(

            f.errors,

            {'__all__': [u'Flatpage with url /myflatpage1 already exists for site example.com']})

    def test_flatpage_admin_form_edit(self):

        """

        Existing flatpages can be edited in the admin form without triggering

        the url-uniqueness validation.

        """

        existing = FlatPage.objects.create(

            url="/myflatpage1", title="Some page", content="The content")

        existing.sites.add(settings.SITE_ID)

        data = dict(url='/myflatpage1', **self.form_data)

        f = FlatpageForm(data=data, instance=existing)

        self.assertTrue(f.is_valid(), f.errors)

        updated = f.save()

        self.assertEqual(updated.title, "A test page")