# apt-get install python3.5 python3.5-dev python3-pip python3-setuptools libjpeg-dev zlib1g-dev libfreetype6-dev liblcms2-dev libwebp-dev tcl8.6-dev tk8.6-dev python-tk socat
$ pip3 install --user --upgrade virtualenv
$ virtualenv -p python3.5 env
$ source env/bin/activate
$ pip3 install -r REQUIREMENTS.txt
$ printenv | grep VIRTUAL_ENV
$ deactivate