fix #5111 AttributeError occured with >=pyOpenSSL-17.2.0 (#5112)
fix #5111 AttributeError occured with >=pyOpenSSL-17.2.0 (#5112)


lmcro/letsencrypt,lmcro/letsencrypt,letsencrypt/letsencrypt,jsha/letsencrypt,stweil/letsencrypt,letsencrypt/letsencrypt,jsha/letsencrypt,stweil/letsencrypt