message: show 404 when None is returned
diff: @@ -234,6 +234,11 @@ pub fn source_browser_handler(req: &mut Request) -> IronResult<Response> {
  };
  let list = FileList::from_path(&conn, &name, &version, &req_path);
  + if list.is_none() {
  + use iron::status;
  + use super::error::Nope;
  + return Err(IronError::new(Nope::NoResults, status::NotFound));
  + }
  let page = Page::new(list)
  .set_bool("show_parent_link", !req_path.is_empty())
  