test REMOTE_USER does not authenticate

if external (and all other methods) are missing  this test ensures
that  a request with REMOTE_USER set  that the token would come
through as unauthenticated

Change-Id: I08a0117773bd4efd8e220306de7ba82df73f7403

keystone/tests/test_v3_auth.py

@@ -2373,6 +2373,23 @@ class TestAuthJSON(test_v3.RestfulTestCase):
         self.post('/auth/tokens', body=auth_data, expected_status=401)
 
 
+class TestAuthJSONExternal(test_v3.RestfulTestCase):
+    content_type = 'json'
+
+    def config_overrides(self):
+        self.config_fixture.config(group='auth', methods='')
+
+    def test_remote_user_no_method(self):
+        api = auth.controllers.Auth()
+        context, auth_info, auth_context = self.build_external_auth_request(
+            self.default_domain_user['name'])
+        self.assertRaises(exception.Unauthorized,
+                          api.authenticate,
+                          context,
+                          auth_info,
+                          auth_context)
+
+
 class TestAuthXML(TestAuthJSON):
     content_type = 'xml'