Log Message:
Update security/py-certbot to 0.18.2.

- An issue where Certbot's ACME module would raise an AttributeError
  trying to create self-signed certificates when used with pyOpenSSL
  17.3.0 has been resolved. For Certbot users with this version of
  pyOpenSSL, this caused Certbot to crash when performing a TLS SNI
  challenge or when the Nginx plugin tried to create an SSL server
  block.