Make sure pages are unpublished before delete

Fixes #570

Conflicts:
	wagtail/wagtailcore/models.py

wagtail/wagtailadmin/views/pages.py

@@ -362,10 +362,6 @@ def delete(request, page_id):
         raise PermissionDenied
 
     if request.POST:
-        if page.live:
-            # Unpublish the page
-            page.unpublish()
-
         parent_id = page.get_parent().id
         page.delete()
 

wagtail/wagtailcore/models.py

@@ -9,6 +9,8 @@ from modelcluster.models import ClusterableModel
 
 from django.db import models, connection, transaction
 from django.db.models import get_model, Q
+from django.db.models.signals import pre_delete
+from django.dispatch.dispatcher import receiver
 from django.http import Http404
 from django.core.cache import cache
 from django.core.handlers.wsgi import WSGIRequest
@@ -894,6 +896,13 @@ def get_navigation_menu_items():
         return []
 
 
+@receiver(pre_delete, sender=Page)
+def unpublish_page_before_delete(sender, instance, **kwargs):
+    # Make sure pages are unpublished before deleting
+    if instance.live:
+        instance.unpublish()
+
+
 class Orderable(models.Model):
     sort_order = models.IntegerField(null=True, blank=True, editable=False)
     sort_order_field = 'sort_order'