Sorry, this is a bug in Certbot. There’s a pending fix at https://github.com/certbot/certbot/pull/3165.
You may be able to apply that patch locally if you find your local copy of acme/acme/client.py.
Actually, looking again at where this error happens, it’s after Certbot has updated your email. So I think your update was successful even though Certbot errored out afterwards.