Lately, I was working on securing one of the website’s through Let’s Encrypt and during I encountered the following error while running “./letsencrypt-auto

Checking for new version...
Creating virtual environment...
./letsencrypt-auto: line 455: virtualenv: command not found

It was on CentOS 6.7 hosted with DigitalOcean and this is how I fixed.

Ensure you have root privilege and execute the following command.

yum install centos-release-SCL
yum update
yum install scl-utils python27 python27-scldevel
scl enable python27 bash

Afterward, I was able to proceed with Let’s Encrypt setup.

Reference: https://community.letsencrypt.org/t/solved-virtualenv-command-not-found/2127/8