jruby was complaining about mixing utf-8 and ascii so don't bother printing error message
I'm not sure why I'm worrying about rubinius - don't officially support it
just test with latest jruby (which is 1.9 mode)
Open3 seems to be buggy in JRuby, so go back to backticks just for jruby
ruby 1.8.7 compatibility
ruby 1.9.2 compatibility