Fixed #16905 -- Added extensible checks (nee validation) framework

This is the result of Christopher Medrela's 2013 Summer of Code project.

Thanks also to Preston Holmes, Tim Graham, Anssi Kääriäinen, Florian
Apolloner, and Alex Gaynor for review notes along the way.

Also: Fixes #8579, fixes #3055, fixes #19844.

1 files changed, 5 insertions, 1 deletions

diff --git a/django/contrib/admin/__init__.py b/django/contrib/admin/__init__.py
index d8fc12e0a5..530badf1df 100644
--- a/django/contrib/admin/__init__.py
+++ b/django/contrib/admin/__init__.py
@@ -1,13 +1,15 @@
 # ACTION_CHECKBOX_NAME is unused, but should stay since its import from here
 # has been referenced in documentation.
+from django.contrib.admin.checks import check_admin_app
 from django.contrib.admin.decorators import register
 from django.contrib.admin.helpers import ACTION_CHECKBOX_NAME
 from django.contrib.admin.options import ModelAdmin, HORIZONTAL, VERTICAL
 from django.contrib.admin.options import StackedInline, TabularInline
-from django.contrib.admin.sites import AdminSite, site
 from django.contrib.admin.filters import (ListFilter, SimpleListFilter,
     FieldListFilter, BooleanFieldListFilter, RelatedFieldListFilter,
     ChoicesFieldListFilter, DateFieldListFilter, AllValuesFieldListFilter)
+from django.contrib.admin.sites import AdminSite, site
+from django.core import checks
 from django.utils.module_loading import autodiscover_modules
 
 __all__ = [
@@ -21,3 +23,5 @@ __all__ = [
 
 def autodiscover():
     autodiscover_modules('admin', register_to=site)
+
+checks.register('admin')(check_admin_app)