Shells player with the provided filename.

            `filename`
                Filename for sound file.

def _play_sound(self, filename):
        """ Shells player with the provided filename.

            `filename`
                Filename for sound file.
            """

        command = self._get_external_player()
        if not command:
            return  # no player found

        if common.IS_MACOSX:
            command += ' "{0}"'.format(filename)
        else:
            # append quiet flag and filename
            is_play = (command == 'play')
            command += ' -q "{0}"'.format(filename)

            # HACK: play can default to using pulseaudio. here, we
            # check if pulse command exists and delegate to alsa if
            # not
            if is_play and not common.which('pulseaudio'):
                command += ' -t alsa'

        # play sound file, ignore if it fails
        common.shell_process(command, background=True)