/opt/eff.org/certbot/venv/lib/python2.6/site-packages/cryptography/init.py:26: DeprecationWarning: Python 2.6 is no longer supported by the Python core team, please upgrade your Python. A future version of cryptography will drop support for Python 2.6
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator standalone, Installer None
Obtaining a new certificate
/opt/eff.org/certbot/venv/lib/python2.6/site-packages/acme/jose/jwa.py:110: DeprecationWarning: signer and verifier have been deprecated. Please use sign and verify instead.
signer = key.signer(self.padding, self.hash)
Performing the following challenges:
tls-sni-01 challenge for ABC.com
tls-sni-01 challenge for www.ABC.com
Cleaning up challenges
Problem binding to port 443: Could not bind to IPv4 or IPv6.