Fixed #26013 -- Moved django.core.urlresolvers to django.urls.

Thanks to Tim Graham for the review.

docs/ref/contrib/admin/index.txt

@@ -1252,7 +1252,7 @@ subclass::
     For example::
 
         from django.contrib import admin
-        from django.core.urlresolvers import reverse
+        from django.urls import reverse
 
         class PersonAdmin(admin.ModelAdmin):
             def view_on_site(self, obj):
@@ -2883,9 +2883,9 @@ So - if you wanted to get a reference to the Change view for a particular
 ``Choice`` object (from the polls application) in the default admin, you would
 call::
 
-    >>> from django.core import urlresolvers
+    >>> from django.urls import reverse
     >>> c = Choice.objects.get(...)
-    >>> change_url = urlresolvers.reverse('admin:polls_choice_change', args=(c.id,))
+    >>> change_url = reverse('admin:polls_choice_change', args=(c.id,))
 
 This will find the first registered instance of the admin application
 (whatever the instance name), and resolve to the view for changing
@@ -2896,8 +2896,7 @@ that instance as a ``current_app`` hint to the reverse call. For example,
 if you specifically wanted the admin view from the admin instance named
 ``custom``, you would need to call::
 
-    >>> change_url = urlresolvers.reverse('admin:polls_choice_change',
-    ...                                   args=(c.id,), current_app='custom')
+    >>> change_url = reverse('admin:polls_choice_change', args=(c.id,), current_app='custom')
 
 For more details, see the documentation on :ref:`reversing namespaced URLs
 <topics-http-reversing-url-namespaces>`.

docs/ref/contrib/sitemaps.txt

@@ -300,13 +300,12 @@ Sitemap for static views
 
 Often you want the search engine crawlers to index views which are neither
 object detail pages nor flatpages. The solution is to explicitly list URL
-names for these views in ``items`` and call
-:func:`~django.core.urlresolvers.reverse` in the ``location`` method of
-the sitemap. For example::
+names for these views in ``items`` and call :func:`~django.urls.reverse` in
+the ``location`` method of the sitemap. For example::
 
     # sitemaps.py
     from django.contrib import sitemaps
-    from django.core.urlresolvers import reverse
+    from django.urls import reverse
 
     class StaticViewSitemap(sitemaps.Sitemap):
         priority = 0.5

docs/ref/contrib/syndication.txt

@@ -53,7 +53,7 @@ This simple example, taken from a hypothetical police beat news site describes
 a feed of the latest five news items::
 
     from django.contrib.syndication.views import Feed
-    from django.core.urlresolvers import reverse
+    from django.urls import reverse
     from policebeat.models import NewsItem
 
     class LatestEntriesFeed(Feed):