Warn install users that future versions of certbot will automatically redirect (#6976)

First step of #6960.

* Warn install users that future versions of certbot will automatically redirect

* Only warn when the user declines or auto-declines redirect

* Unit tests

* Update changelog

certbot/client.py

@@ -549,6 +549,11 @@ class Client(object):
                 if ask_redirect:
                     if config_name == "redirect" and config_value is None:
                         config_value = enhancements.ask(enhancement_name)
+                        if not config_value:
+                            logger.warning("Future versions of Certbot will automatically "
+                                "configure the webserver so that all requests redirect to secure "
+                                "HTTPS access. You can control this behavior and disable this "
+                                "warning with the --redirect and --no-redirect flags.")
                 if config_value:
                     self.apply_enhancement(domains, enhancement_name, option)
                     enhanced = True

certbot/tests/client_test.py

@@ -564,6 +564,21 @@ class EnhanceConfigTest(ClientTestCommon):
         self.assertEqual(mock_log.warning.call_args[0][1],
                           'redirect')
 
+    @mock.patch("certbot.client.logger")
+    def test_config_set_no_warning_redirect(self, mock_log):
+        self.config.redirect = False
+        self._test_with_already_existing()
+        self.assertFalse(mock_log.warning.called)
+
+    @mock.patch("certbot.client.enhancements.ask")
+    @mock.patch("certbot.client.logger")
+    def test_warn_redirect(self, mock_log, mock_ask):
+        self.config.redirect = None
+        mock_ask.return_value = False
+        self._test_with_already_existing()
+        self.assertTrue(mock_log.warning.called)
+        self.assertTrue("disable" in mock_log.warning.call_args[0][0])
+
     def test_no_ask_hsts(self):
         self.config.hsts = True
         self._test_with_all_supported()