unstable(JRUBY-4171,linux,intermittent failure):IO.popen writes to a write-only pipe
fails:IO.popen starts returns a forked process if the command is -
fails(JRUBY-5663):IO.popen with a leading Array parameter uses a trailing Hash in the Array for spawn-like settings
fails:IO.popen does not throw an exception if child exited and has been waited for
