When python3 is missing from the host operating system, the install.sh
and install-dev.sh scripts fail with the following error:

    Creating virtual environment in /home/centos/kayobe-venv
    /home/centos/kayobe/dev/functions: line 169: python3: command not found

Change-Id: I50d47ceeeae803545d78a40bbeec1aaa2f5112b1