def normalize_rss(rss)
      return rss if maybe_xml?(rss)

      uri = to_uri(rss)

      if uri.respond_to?(:read)
        uri.read
      elsif !rss.tainted? and File.readable?(rss)
        File.open(rss) {|f| f.read}
      else
        rss
      end
    end
def normalize_rss(rss)
      return rss if maybe_xml?(rss)

      uri = to_uri(rss)

      if uri.respond_to?(:read)
        uri.read
      elsif !rss.tainted? and File.readable?(rss)
        File.open(rss) {|f| f.read}
      else
        rss
      end
    end
Try to get the XML associated with +rss+.
 Return +rss+ if it already looks like XML, or treat it as a URI,
 or a file to get the XML,