'L{SSHUserAuthClient.getPrivateKey} will load a private key from the
last used file populated by L{SSHUserAuthClient.getPublicKey}, and
return a L{Deferred} which fires with the corresponding private L{Key}.'

def test_getPrivateKey(self):

    rsaPrivate = Key.fromString(keydata.privateRSA_openssh)
    options = ConchOptions()
    options.identitys = [self.rsaFile.path]
    client = SSHUserAuthClient('user', options, None)
    client.getPublicKey()
    def _cbGetPrivateKey(key):
        self.assertFalse(key.isPublic())
        self.assertEqual(key, rsaPrivate)
    return client.getPrivateKey().addCallback(_cbGetPrivateKey)
