Render the message template in case of error instead of redirecting

Especially since we are redirecting to a package_info page for a package
that we didn't find.
Non-packagers can ask for watch* ACLs

So let's only check that the user is a packager for the other ACLs
Add unit-tests for the request_acl_all_branch method
Add unit-tests for the giveup_acl method