misc: use page with slug 404 for 404 error pages (#22764)

combo/public/views.py

@@ -408,10 +408,15 @@ def error404(request, *args, **kwargs):
         # when the given hostname doesn't exist as a tenant
         from django.views.defaults import page_not_found
         return page_not_found(request, *args, **kwargs)
-    page = Page()
-    page.template_name = 'standard'
-    return publish_page(request, page, status=404, template_name='combo/404.html')
 
+    try:
+        page = Page.objects.get(slug='404')
+        template_name = None
+    except Page.DoesNotExist:
+        page = Page()
+        page.template_name = 'standard'
+        template_name = 'combo/404.html'
+    return publish_page(request, page, status=404, template_name=template_name)
 
 def menu_badges(request):
     context = {'request': request}

tests/test_public.py

@@ -267,6 +267,12 @@ def test_404(app):
     resp = app.get('/foobar/', status=404)
     assert "This page doesn't exist" in resp.body
 
+    page = Page(title='Not Found', slug='404', template_name='standard')
+    page.save()
+    TextCell(page=page, placeholder='content', text='Custom 404 Text', order=0).save()
+    resp = app.get('/foobar/', status=404)
+    assert 'Custom 404 Text' in resp.body
+
 def test_style_demo(app, admin_user):
     TextCell.objects.all().delete()
     Page.objects.all().delete()