Hello @Ray,
Remove the virtualenv, update letsencrypt client and try again.
Viewing the logs seems you have letsencrypt installed on /root/letsencrypt/ so my examples will use it:
1.- Backup and remove virtualenv
cd /root/
tar zcvf backup-local-letsencrypt.tar.gz /root/.local/share/letsencrypt/
rm -rf /root/.local/share/letsencrypt/
2.- Update letsencrypt.
If you installed letsencrypt using git clone go to the dir where it is installed and perform a git pull
cd /root/letsencrypt/
git pull
3.- Recreate the virtualenv
To recreate the virtualenv just launch letsencrypt-auto command, it will check the system depencies and will install all you need.
cd /root/letsencrypt/
./letsencrypt-auto
If after that you get the same cffi error, check this post
Cheers,
sahsanu