module Mixlib::ShellOut::Unix

def propagate_pre_exec_failure

assume everything went well.
If it's there, un-marshal it and raise. If it's not there,
Attempt to get a Marshaled error from the side-channel. 
def propagate_pre_exec_failure
  begin
    attempt_buffer_read until child_process_status.eof?
    e = Marshal.load(@process_status)
    raise(Exception === e ? e : "unknown failure: #{e.inspect}")
  rescue ArgumentError # If we get an ArgumentError error, then the exec was successful

    true
  ensure
    child_process_status.close
    open_pipes.delete(child_process_status)
  end
end