'The return value of L{formatFailure} is a C{str} instance (not a
C{unicode} instance) with numeric character references for any non-ASCII
characters meant to appear in the output.'

def test_returnsBytes(self):

    try:
        raise Exception('Fake    bug')
    except:
        result = formatFailure(Failure())
    self.assertIsInstance(result, bytes)
    if _PY3:
        self.assertTrue(all(((ch < 128) for ch in result)))
    else:
        self.assertTrue(all(((ord(ch) < 128) for ch in result)))
    self.assertIn('&#160;', result)
