def test_saveKeyNoFilename(self):
        """
        When no path is specified, it will ask for the path used to store the
        key.
        """
        base = FilePath(self.mktemp())
        base.makedirs()
        keyPath = base.child('custom_key').path

        import twisted.conch.scripts.ckeygen
        self.patch(twisted.conch.scripts.ckeygen, 'raw_input', lambda _: keyPath)
        key = Key.fromString(privateRSA_openssh)
        _saveKey(key, {'filename': None, 'no-passphrase': True,
            'format': 'md5-hex'})

        persistedKeyContent = base.child('custom_key').getContent()
        persistedKey = key.fromString(persistedKeyContent, None, b'')
        self.assertEqual(key, persistedKey)

        When no path is specified, it will ask for the path used to store the
        key.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_ckeygen.py