Fixed #28593 -- Added a simplified URL routing syntax per DEP 0201.

Thanks Aymeric Augustin for shepherding the DEP and patch review.
Thanks Marten Kenbeek and Tim Graham for contributing to the code.
Thanks Tom Christie, Shai Berger, and Tim Graham for the docs.

docs/ref/contrib/admin/admindocs.txt

@@ -19,9 +19,9 @@ To activate the :mod:`~django.contrib.admindocs`, you will need to do
 the following:
 
 * Add :mod:`django.contrib.admindocs` to your :setting:`INSTALLED_APPS`.
-* Add ``url(r'^admin/doc/', include('django.contrib.admindocs.urls'))`` to
+* Add ``path('admin/doc/', include('django.contrib.admindocs.urls'))`` to
   your ``urlpatterns``. Make sure it's included *before* the
-  ``r'^admin/'`` entry, so that requests to ``/admin/doc/`` don't get
+  ``'admin/'`` entry, so that requests to ``/admin/doc/`` don't get
   handled by the latter entry.
 * Install the docutils Python module (http://docutils.sf.net/).
 * **Optional:** Using the admindocs bookmarklets requires

docs/ref/contrib/admin/index.txt

@@ -1587,11 +1587,15 @@ templates used by the :class:`ModelAdmin` views:
     that ModelAdmin in the same way as a URLconf.  Therefore you can extend
     them as documented in :doc:`/topics/http/urls`::
 
+        from django.contrib import admin
+        from django.template.response import TemplateResponse
+        from django.urls import path
+
         class MyModelAdmin(admin.ModelAdmin):
             def get_urls(self):
                 urls = super().get_urls()
                 my_urls = [
-                    url(r'^my_view/$', self.my_view),
+                    path('my_view/', self.my_view),
                 ]
                 return my_urls + urls
 
@@ -1643,13 +1647,13 @@ templates used by the :class:`ModelAdmin` views:
             def get_urls(self):
                 urls = super().get_urls()
                 my_urls = [
-                    url(r'^my_view/$', self.admin_site.admin_view(self.my_view))
+                    path('my_view/', self.admin_site.admin_view(self.my_view))
                 ]
                 return my_urls + urls
 
     Notice the wrapped view in the fifth line above::
 
-        url(r'^my_view/$', self.admin_site.admin_view(self.my_view))
+        path('my_view/', self.admin_site.admin_view(self.my_view))
 
     This wrapping will protect ``self.my_view`` from unauthorized access and
     will apply the :func:`django.views.decorators.cache.never_cache` decorator to
@@ -1659,7 +1663,7 @@ templates used by the :class:`ModelAdmin` views:
     performed, you can pass a ``cacheable=True`` argument to
     ``AdminSite.admin_view()``::
 
-        url(r'^my_view/$', self.admin_site.admin_view(self.my_view, cacheable=True))
+        path('my_view/', self.admin_site.admin_view(self.my_view, cacheable=True))
 
     ``ModelAdmin`` views have ``model_admin`` attributes. Other
     ``AdminSite`` views have ``admin_site`` attributes.
@@ -2767,17 +2771,17 @@ Hooking ``AdminSite`` instances into your URLconf
 The last step in setting up the Django admin is to hook your ``AdminSite``
 instance into your URLconf. Do this by pointing a given URL at the
 ``AdminSite.urls`` method. It is not necessary to use
-:func:`~django.conf.urls.include()`.
+:func:`~django.urls.include()`.
 
 In this example, we register the default ``AdminSite`` instance
 ``django.contrib.admin.site`` at the URL ``/admin/`` ::
 
     # urls.py
-    from django.conf.urls import url
     from django.contrib import admin
+    from django.urls import path
 
     urlpatterns = [
-        url(r'^admin/', admin.site.urls),
+        path('admin/', admin.site.urls),
     ]
 
 .. _customizing-adminsite:
@@ -2809,12 +2813,12 @@ update :file:`myproject/urls.py` to reference your :class:`AdminSite` subclass.
 .. snippet::
     :filename: myproject/urls.py
 
-    from django.conf.urls import url
+    from django.urls import path
 
     from myapp.admin import admin_site
 
     urlpatterns = [
-        url(r'^myadmin/', admin_site.urls),
+        path('myadmin/', admin_site.urls),
     ]
 
 Note that you may not want autodiscovery of ``admin`` modules when using your
@@ -2838,12 +2842,12 @@ separate versions of the admin site -- using the ``AdminSite`` instances
 respectively::
 
     # urls.py
-    from django.conf.urls import url
+    from django.urls import path
     from myproject.admin import basic_site, advanced_site
 
     urlpatterns = [
-        url(r'^basic-admin/', basic_site.urls),
-        url(r'^advanced-admin/', advanced_site.urls),
+        path('basic-admin/', basic_site.urls),
+        path('advanced-admin/', advanced_site.urls),
     ]
 
 ``AdminSite`` instances take a single argument to their constructor, their
@@ -2879,23 +2883,23 @@ your URLconf. Specifically, add these four patterns::
 
     from django.contrib.auth import views as auth_views
 
-    url(
-        r'^admin/password_reset/$',
+    path(
+        'admin/password_reset/',
         auth_views.PasswordResetView.as_view(),
         name='admin_password_reset',
     ),
-    url(
-        r'^admin/password_reset/done/$',
+    path(
+        'admin/password_reset/done/',
         auth_views.PasswordResetDoneView.as_view(),
         name='password_reset_done',
     ),
-    url(
-        r'^reset/(?P<uidb64>[0-9A-Za-z_\-]+)/(?P<token>.+)/$',
+    path(
+        'reset/<uidb64>/<token>/',
         auth_views.PasswordResetConfirmView.as_view(),
         name='password_reset_confirm',
     ),
-    url(
-        r'^reset/done/$',
+    path(
+        'reset/done/',
         auth_views.PasswordResetCompleteView.as_view(),
         name='password_reset_complete',
     ),