Obviously not the best way to test for this, but I didn't want to
involve a regexp or a dom parser. The old way didn't work for our app or
any app that puts attributes on html (like facebook open graph
in my case response was invoked with the send_file command:
send_file "/tmp/myfile.zip", :type => 'application/zip', :filename=>'myfile.zip'
looks that it's bad to call response.body if response is ActionDispatch::Response