[1.7.x] Fixed #24097 -- Prevented AttributeError in redirect_to_login

Thanks Peter Schmidt for the report and the initial patch.
Thanks to Oktay Sancak for writing the original failing test and
Alvin Savoy for supporting contributing back to the community.
Backport of d7bc37d61 from master.

django/shortcuts.py

@@ -11,6 +11,8 @@ from django.db.models.manager import Manager
 from django.db.models.query import QuerySet
 from django.core import urlresolvers
 from django.utils import six
+from django.utils.encoding import force_text
+from django.utils.functional import Promise
 
 
 def render_to_response(*args, **kwargs):
@@ -148,6 +150,11 @@ def resolve_url(to, *args, **kwargs):
     if hasattr(to, 'get_absolute_url'):
         return to.get_absolute_url()
 
+    if isinstance(to, Promise):
+        # Expand the lazy instance, as it can cause issues when it is passed
+        # further to some Python functions like urlparse.
+        to = force_text(to)
+
     if isinstance(to, six.string_types):
         # Handle relative URLs
         if any(to.startswith(path) for path in ('./', '../')):