add catch for http error on invite token check

app/main/views/invites.py

@@ -1,6 +1,7 @@
 from flask import abort, flash, redirect, render_template, session, url_for
 from flask_login import current_user
 from markupsafe import Markup
+from notifications_python_client.errors import HTTPError
 
 from app import (
     invite_api_client,
@@ -14,7 +15,14 @@ from app.main import main
 
 @main.route("/invitation/<token>")
 def accept_invite(token):
-    invited_user = invite_api_client.check_token(token)
+    try:
+        invited_user = invite_api_client.check_token(token)
+    except HTTPError as e:
+        if e.status_code == 400 and 'invitation' in e.message:
+            flash(e.message['invitation'])
+            return redirect(url_for('main.sign_in'))
+        else:
+            raise e
 
     if not current_user.is_anonymous and current_user.email_address.lower() != invited_user.email_address.lower():
         message = Markup("""

tests/app/main/views/test_accept_invite.py

@@ -1,8 +1,10 @@
-from unittest.mock import ANY
+from unittest.mock import ANY, Mock
 
 from bs4 import BeautifulSoup
 from flask import url_for
+from notifications_python_client.errors import HTTPError
 from tests.conftest import mock_check_invite_token as mock_check_token_invite
+from tests.conftest import normalize_spaces
 from tests.conftest import sample_invite as create_sample_invite
 
 import app
@@ -215,6 +217,36 @@ def test_cancelled_invited_user_accepts_invited_redirect_to_cancelled_invitation
     assert page.h1.string.strip() == 'The invitation you were sent has been cancelled'
 
 
+def test_new_user_accept_invite_with_malformed_token(
+    client,
+    service_one,
+    mocker,
+):
+    mocker.patch('app.invite_api_client.check_token', side_effect=HTTPError(
+        response=Mock(
+            status_code=400,
+            json={
+                'result': 'error',
+                'message': {
+                    'invitation': {
+                        'Something’s wrong with this link. Make sure you’ve copied the whole thing.'
+                    }
+                }
+            }
+        ),
+        message={'invitation': 'Something’s wrong with this link. Make sure you’ve copied the whole thing.'}
+    ))
+
+    response = client.get(url_for('main.accept_invite', token='thisisnotarealtoken'), follow_redirects=True)
+
+    assert response.status_code == 200
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+
+    assert normalize_spaces(
+        page.select_one('.banner-dangerous').text
+    ) == 'Something’s wrong with this link. Make sure you’ve copied the whole thing.'
+
+
 def test_new_user_accept_invite_completes_new_registration_redirects_to_verify(
     client,
     service_one,