Python: Create self-signed ssl certificate

ssl.py

def create_ssl_certificate(distinguished_name, key_file, cert_file, overwrite=False, X509=None):
    from OpenSSL import crypto

    if not os.path.exists(cert_file) or not os.path.exists(key_file) or overwrite:
        k = crypto.PKey()
        k.generate_key(crypto.TYPE_RSA, 1024)

        if X509 is None:
            X509 = crypto.X509()
            X509.get_subject().C = "FR"
            X509.get_subject().ST = "Strasbourg"
            X509.get_subject().L = "."
            X509.get_subject().O = "Some stuff"
            X509.get_subject().OU = "Some other stuff"

        X509.get_subject().CN = distinguished_name
        X509.set_serial_number(1)
        X509.gmtime_adj_notBefore(0)
        X509.gmtime_adj_notAfter(315360000)
        X509.set_issuer(X509.get_subject())
        X509.set_pubkey(k)
        X509.sign(k, 'sha1')
        open(cert_file, "wt").write(crypto.dump_certificate(crypto.FILETYPE_PEM, X509).decode('utf-8'))
        open(key_file, "wt").write(crypto.dump_privatekey(crypto.FILETYPE_PEM, k).decode('utf-8'))

    return cert_file, key_file