'If no cluster option and no environment, script fails'

def test_missing_environment(self):

    options = BenchmarkOptions()
    options.parseOptions([])
    with capture_stderr() as captured_stderr:
        exception = self.assertRaises(SystemExit, get_cluster, options, {})
        self.assertIn('not    set', exception.args[0])
        self.assertIn(options.getUsage(), captured_stderr())
