Returns a tar with the runner script.

def tar_runner(self):
        """ Returns a tar with the runner script.
        """
        script_bytes = self.RUNNER.read_bytes()

        tarstream = BytesIO()
        tar = tarfile.TarFile(fileobj=tarstream, mode='w')

        tarinfo = tarfile.TarInfo(name="runner.py")
        tarinfo.size = len(script_bytes)
        tarinfo.mtime = int(time.time())

        tar.addfile(tarinfo, BytesIO(script_bytes))
        tar.close()

        return tarstream.getvalue()