check python version in "pyenv" code example

Example 1: install pyenv

# Linux and Mac only (at the moment)
curl https://pyenv.run | bash

Example 2: pyenv install ubuntu

root@ubuntu:~# apt install -y make build-essential libssl-dev zlib1g-dev \
> libbz2-dev libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev\
> libncursesw5-dev xz-utils tk-dev libffi-dev liblzma-dev python-openssl\
> git