Disable federated login for new users if user creation is disabled

Fixes https://www.pivotaltracker.com/story/show/144821585

data/users/test/test_users.py

@@ -0,0 +1,36 @@
+import pytest
+
+from mock import patch
+
+from data.database import model
+from data.users.federated import DISABLED_MESSAGE
+from test.test_ldap import mock_ldap
+from test.test_keystone_auth import fake_keystone
+
+from test.fixtures import *
+
+@pytest.mark.parametrize('auth_system_builder, user1, user2', [
+  (mock_ldap, ('someuser', 'somepass'), ('testy', 'password')),
+  (fake_keystone, ('cool.user', 'password'), ('some.neat.user', 'foobar')),
+])
+def test_auth_createuser(auth_system_builder, user1, user2, config, app):
+  with auth_system_builder() as auth:
+    # Login as a user and ensure a row in the database is created for them.
+    user, err = auth.verify_and_link_user(*user1)
+    assert err is None
+    assert user
+
+    federated_info = model.user.lookup_federated_login(user, auth.federated_service)
+    assert federated_info is not None
+
+    # Disable user creation.
+    with patch('features.USER_CREATION', False):
+      # Ensure that the existing user can login.
+      user_again, err = auth.verify_and_link_user(*user1)
+      assert err is None
+      assert user_again.id == user.id
+
+      # Ensure that a new user cannot.
+      new_user, err = auth.verify_and_link_user(*user2)
+      assert new_user is None
+      assert err == DISABLED_MESSAGE