Handle 503

fetch': 503 => Net::HTTPServiceUnavailable for
https://rubytapas.dpdcart.com/subscriber/download?file_id=35257 --
unhandled response (Mechanize::ResponseCodeError)
  from
  mechanize-2.6.0/lib/mechanize.rb:431:in `get'
  from lib/downloader/scraper.rb:40:in `get'
(the failing file is loader.rb and it exists.. dunno)