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

Thanks to Tim Graham for the review.

docs/intro/tutorial04.txt

@@ -71,7 +71,7 @@ create a real version. Add the following to ``polls/views.py``:
 
     from django.shortcuts import get_object_or_404, render
     from django.http import HttpResponseRedirect, HttpResponse
-    from django.core.urlresolvers import reverse
+    from django.urls import reverse
 
     from .models import Choice, Question
     # ...
@@ -124,13 +124,13 @@ This code includes a few things we haven't covered yet in this tutorial:
   POST data. This tip isn't specific to Django; it's just good Web
   development practice.
 
-* We are using the :func:`~django.core.urlresolvers.reverse` function in the
+* We are using the :func:`~django.urls.reverse` function in the
   :class:`~django.http.HttpResponseRedirect` constructor in this example.
   This function helps avoid having to hardcode a URL in the view function.
   It is given the name of the view that we want to pass control to and the
   variable portion of the URL pattern that points to that view. In this
   case, using the URLconf we set up in :doc:`Tutorial 3 </intro/tutorial03>`,
-  this :func:`~django.core.urlresolvers.reverse` call will return a string like
+  this :func:`~django.urls.reverse` call will return a string like
   ::
 
     '/polls/3/results/'
@@ -264,7 +264,7 @@ views and use Django's generic views instead. To do so, open the
 
     from django.shortcuts import get_object_or_404, render
     from django.http import HttpResponseRedirect
-    from django.core.urlresolvers import reverse
+    from django.urls import reverse
     from django.views import generic
 
     from .models import Choice, Question