[Review] Request from 'aduffeck' @ 'SUSE/machinery/review_140814_do_not_choke_on_broken_filenames'

Please review the following changes:
  * f36c671 Do not choke on filenames with invalid UTF-8 characters
  * d50bfee DRY up test by specifying a test subject
  * a726e33 Use the same tarball for setting up the machine and the test
  * 9c3eaad Add Machinery::Ui.warn method for printing warnings to the console