Check for tar file that tarfile library mistakenly reports as invalid.
        Happens with tar files created on FAT systems.  See:
        http://stackoverflow.com/questions/25552162/tarfile-readerror-file-could-not-be-opened-successfully

def _is_bugged_tarfile(self):
        """
        Check for tar file that tarfile library mistakenly reports as invalid.
        Happens with tar files created on FAT systems.  See:
        http://stackoverflow.com/questions/25552162/tarfile-readerror-file-could-not-be-opened-successfully
        """
        try:
            output = subprocess.check_output(['file', '-z', self.destination]).decode('utf8')
            return 'tar archive' in output and 'gzip compressed data' in output
        except subprocess.CalledProcessError:
            return False