Redmine

Currently, depending on the filename extension of the attachment (i.e., zip or txt), the named attachment download route sometimes responds to unauthorized requests with a Status 401 instead of a redirect to the login form for unauthorized requests. This leads to an error message about a broken link in the users' browser. The route without filename always correctly redirects to the login form.

The attached patch (courtesy of Planio) forces the format for the named attachment download route to HTML to fix that, so that the routes with filename always redirects to `/login`, as well.