manager: makes sure slug is unique

combo/manager/forms.py

@@ -16,6 +16,8 @@
 
 from django import forms
 from django.conf import settings
+from django.core.exceptions import ValidationError
+from django.utils.translation import ugettext_lazy as _
 
 from combo.data.models import Page
 
@@ -30,6 +32,14 @@ class PageForm(forms.ModelForm):
         templates.sort(lambda x, y: cmp(x[1], y[1]))
         self.fields['template_name'].widget = forms.Select(choices=templates)
 
+    def clean_slug(self):
+        value = self.cleaned_data.get('slug')
+        if self.instance.slug == value:
+            return value
+        if Page.objects.filter(slug=value).count() > 0:
+            raise ValidationError(_('Slug must be unique'), code='unique')
+        return value
+
 class PageEditForm(PageForm):
     class Meta:
         model = Page