Ensure that the `enclosure_url` is curl-able and not escaping the ampersand.

economist_enclosures.rb

require 'feedzirra'

feed = Feedzirra::Feed.fetch_and_parse('http://www.economist.com/media/rss/economist.xml')
entries = feed.entries

curls = entries.map do |entry|
  curl = `curl --head #{entry.enclosure_url}`
  curl.split(/\r/).first
end

puts "\n\n\n"
puts curls.uniq

entries.each do |entry|
  puts entry.enclosure_url
end

puts "\n\n\n"
puts entries.select { |entry| entry.enclosure_url.match /\&amp\;/ }.count