From e81f30208433ef7d3691119293e6978cadc866a3 Mon Sep 17 00:00:00 2001
From: Leo Hemsted <leo.hemsted@digital.cabinet-office.gov.uk>
Date: Fri, 22 Jun 2018 17:36:58 +0100
Subject: [PATCH] handle 405 METHOD NOT ALLOWEDs

(show the "something went wrong" error page).

also catch any other werkzeug http exceptions and show an appropriate
template, if it exists
---
 app/__init__.py                      | 21 ++++++++++++++++-----
 tests/app/main/test_errorhandlers.py |  8 ++++++++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/app/__init__.py b/app/__init__.py
index 3f2d11606..ee6a4a899 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -34,9 +34,8 @@ from notifications_utils.recipients import (
 )
 from notifications_utils.formatters import formatted_list
 from notifications_utils.sanitise_text import SanitiseASCII
-from werkzeug.exceptions import abort
+from werkzeug.exceptions import abort, HTTPException as WerkzeugHTTPException
 from werkzeug.local import LocalProxy
-from werkzeug.routing import RequestRedirect
 
 from app import proxy_fix
 from app.config import configs
@@ -584,9 +583,21 @@ def register_errorhandlers(application):  # noqa (C901 too complex)
         ), 400)
         return useful_headers_after_request(resp)
 
-    @application.errorhandler(RequestRedirect)
-    def handle_301(error):
-        return error
+    @application.errorhandler(405)
+    def handle_405(error):
+        resp = make_response(render_template(
+            "error/400.html",
+            message=['Something went wrong, please go back and try again.']
+        ), 405)
+        return useful_headers_after_request(resp)
+
+    @application.errorhandler(WerkzeugHTTPException)
+    def handle_http_error(error):
+        if error.code == 301:
+            # RequestRedirect exception
+            return error
+
+        return _error_response(error.code)
 
     @application.errorhandler(500)
     @application.errorhandler(Exception)
diff --git a/tests/app/main/test_errorhandlers.py b/tests/app/main/test_errorhandlers.py
index 770efbbdf..1b36bcbbc 100644
--- a/tests/app/main/test_errorhandlers.py
+++ b/tests/app/main/test_errorhandlers.py
@@ -60,3 +60,11 @@ def test_csrf_redirects_to_sign_in_page_if_not_signed_in(client, mocker):
 
     assert response.status_code == 302
     assert response.location == url_for('main.sign_in', next='/cookies', _external=True)
+
+
+def test_405_returns_something_went_wrong_page(client, mocker):
+    response = client.post('/')
+
+    assert response.status_code == 405
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+    assert page.h1.string.strip() == 'Something went wrong, please go back and try again.'