typing: Add assertions for Optional values.

Signed-off-by: Zixuan James Li <p359101898@gmail.com>

zerver/models.py

@@ -3795,6 +3795,7 @@ def bot_owner_user_ids(user_profile: UserProfile) -> Set[int]:
         and user_profile.default_events_register_stream.invite_only
     )
     if is_private_bot:
+        assert user_profile.bot_owner_id is not None
         return {user_profile.bot_owner_id}
     else:
         users = {user.id for user in user_profile.realm.get_human_admin_users()}

zerver/tests/test_link_embed.py

@@ -403,6 +403,7 @@ class PreviewTestCase(ZulipTestCase):
 
         # Verify the initial message doesn't have the embedded links rendered
         msg = Message.objects.select_related("sender").get(id=msg_id)
+        assert msg.rendered_content is not None
         self.assertNotIn(f'<a href="{url}" title="The Rock">The Rock</a>', msg.rendered_content)
 
         self.create_mock_response(url, relative_url=relative_url)
@@ -449,6 +450,7 @@ class PreviewTestCase(ZulipTestCase):
                 in info_logs.output[0]
             )
             msg = Message.objects.select_related("sender").get(id=msg_id)
+            assert msg.rendered_content is not None
             # The content of the message has changed since the event for original_url has been created,
             # it should not be rendered. Another, up-to-date event will have been sent (edited_url).
             self.assertNotIn(