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

Thanks to Tim Graham for the review.

django/__init__.py

@@ -15,7 +15,7 @@ def setup(set_prefix=True):
     """
     from django.apps import apps
     from django.conf import settings
-    from django.core.urlresolvers import set_script_prefix
+    from django.urls import set_script_prefix
     from django.utils.encoding import force_text
     from django.utils.log import configure_logging