unsubscribe: Use get_object_from_key for confirmation.

This is the only one of the confirmation pathways that wasn't using this
idiom, I think.

confirmation/models.py

@@ -18,7 +18,7 @@ from django.utils.timezone import now as timezone_now
 
 from zerver.lib.send_email import send_email
 from zerver.lib.utils import generate_random_token
-from zerver.models import PreregistrationUser, EmailChangeStatus, MultiuseInvite
+from zerver.models import PreregistrationUser, EmailChangeStatus, MultiuseInvite, UserProfile
 from random import SystemRandom
 import string
 from typing import Any, Dict, Optional, Text, Union
@@ -48,7 +48,7 @@ def generate_key():
     return ''.join(generator.choice(string.ascii_lowercase + string.digits) for _ in range(24))
 
 def get_object_from_key(confirmation_key, confirmation_type):
-    # type: (str, int) -> Union[MultiuseInvite, PreregistrationUser, EmailChangeStatus]
+    # type: (str, int) -> Union[MultiuseInvite, PreregistrationUser, EmailChangeStatus, UserProfile]
     # Confirmation keys used to be 40 characters
     if len(confirmation_key) not in (24, 40):
         raise ConfirmationKeyException(ConfirmationKeyException.WRONG_LENGTH)

zerver/tests/test_signup.py

@@ -863,9 +863,9 @@ so we didn't send them an invitation. We did send invitations to everyone else!"
         # type: () -> None
         user = self.example_user('hamlet')
         registration_key = create_confirmation_link(user, 'host', Confirmation.USER_REGISTRATION).split('/')[-1]
-        with self.assertRaises(ConfirmationKeyException) as exception:
+        with self.assertRaises(ConfirmationKeyException) as cm:
             get_object_from_key(registration_key, Confirmation.INVITATION)
-            self.assertEqual(exception.error_type, ConfirmationKeyException.DOES_NOT_EXIST)
+        self.assertEqual(cm.exception.error_type, ConfirmationKeyException.DOES_NOT_EXIST)
 
 class InvitationsTestCase(InviteUserBase):
     def test_successful_get_open_invitations(self):
@@ -1107,9 +1107,10 @@ class EmailUnsubscribeTests(ZulipTestCase):
     def test_error_unsubscribe(self):
         # type: () -> None
 
-        # An invalid insubscribe token "test123" produces an error.
+        # An invalid insubscribe token "test123" produces an error, in this
+        # case, a link malformed error.
         result = self.client_get('/accounts/unsubscribe/missed_messages/test123')
-        self.assert_in_response('Unknown email unsubscribe request', result)
+        self.assert_in_response('Make sure you copied the link', result)
 
         # An unknown message type "fake" produces an error.
         user_profile = self.example_user('hamlet')

zerver/views/unsubscribe.py

@@ -4,19 +4,19 @@ from django.http import HttpRequest, HttpResponse
 from django.shortcuts import render
 from typing import Callable
 
-from confirmation.models import Confirmation
+from confirmation.models import Confirmation, get_object_from_key, \
+    render_confirmation_key_error, ConfirmationKeyException
 from zerver.lib.actions import do_change_notification_settings, clear_scheduled_emails
 from zerver.models import UserProfile, ScheduledEmail
 from zerver.context_processors import common_context
 
-def process_unsubscribe(request: HttpRequest, token: str, subscription_type: str,
+def process_unsubscribe(request: HttpRequest, confirmation_key: str, subscription_type: str,
                         unsubscribe_function: Callable[[UserProfile], None]) -> HttpResponse:
     try:
-        confirmation = Confirmation.objects.get(confirmation_key=token)
-    except Confirmation.DoesNotExist:
-        return render(request, 'zerver/unsubscribe_link_error.html')
+        user_profile = get_object_from_key(confirmation_key, Confirmation.UNSUBSCRIBE)
+    except ConfirmationKeyException as exception:
+        return render_confirmation_key_error(request, exception)
 
-    user_profile = confirmation.content_object
     unsubscribe_function(user_profile)
     context = common_context(user_profile)
     context.update({"subscription_type": subscription_type})