Description of problem:


Version-Release number of selected component (if applicable):
25.6

How reproducible:
easily

Steps to Reproduce:
1. Click https://$YOURBEAKER/tasks/no/such/task

Actual results:
You just get a 302 redirect back to /tasks with no error message.

Expected results:
Response code should be a 404, there should be an error message

Additional info:
Historically a lot of old TG pages would redirect somewhere with a flash message saying "No such blah" instead of just giving a plain 404 with a sensible error message. Most likely this code is trying to do that but since /tasks is not use Turbogears anymore the flash message is not shown.

In general we should be switching towards the more conventional (and semantic) response of 404 with a good error, instead of redirecting with flash messages.