':py:obj:`load_privatekey` can create a :py:obj:`PKey` object from an encrypted PEM
string if given a passphrase callback which returns the correct
password.'

def test_load_privatekey_passphraseCallback(self):

    called = []
    def cb(writing):
        called.append(writing)
        return encryptedPrivateKeyPEMPassphrase
    key = load_privatekey(FILETYPE_PEM, encryptedPrivateKeyPEM, cb)
    self.assertTrue(isinstance(key, PKeyType))
    self.assertEqual(called, [False])
