'Don\'t validate the same response twice.
From "Checking the Nonce"::
When using "check_authentication", the OP MUST ensure that an
assertion has not yet been accepted with the same value for
"openid.response_nonce".
In this implementation, the assoc_handle is only valid once.  And
nonces are a signed component of the message, so they can\'t be used
with another handle without breaking the sig.'

def test_replay(self):

    r = self.request.answer(self.signatory)
    r = self.request.answer(self.signatory)
    self.failUnlessEqual(r.fields.getArgs(OPENID_NS), {'is_valid': 'false'})
