def test_missingCertificateFile(self):
        """
        Instantiating L{ssl.DefaultOpenSSLContextFactory} with a certificate
        filename which does not identify an existing file results in the
        initializer raising L{OpenSSL.SSL.Error}.
        """
        self.assertRaises(
            SSL.Error,
            ssl.DefaultOpenSSLContextFactory, certPath, self.mktemp())

        Instantiating L{ssl.DefaultOpenSSLContextFactory} with a certificate
        filename which does not identify an existing file results in the
        initializer raising L{OpenSSL.SSL.Error}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_ssl.py