Raise (pending) deprecation warning for allow_syncdb.

django/db/utils.py

@@ -268,6 +268,10 @@ class ConnectionRouter(object):
                 try:
                     method = router.allow_migrate
                 except AttributeError:
+                    warnings.warn(
+                        'Router.allow_syncdb has been deprecated and will stop working in Django 1.9.'
+                        'Rename the method to allow_migrate.',
+                        PendingDeprecationWarning, stacklevel=2)
                     method = router.allow_syncdb
             except AttributeError:
                 # If the router doesn't have a method, skip to the next one.