4 images: ['litmusimage/debian:8']
7 images: ['centos/7', 'generic/ubuntu1804']
10 images: ['litmusimage/debian:9', 'litmusimage/debian:10']
13 images: ['litmusimage/ubuntu:16.04', 'litmusimage/ubuntu:18.04']
16 images: ['litmusimage/ubuntu:16.04', 'litmusimage/ubuntu:18.04', 'litmusimage/ubuntu:20.04']
25 images: ['debian-8-x86_64', 'debian-9-x86_64', 'debian-10-x86_64', 'ubuntu-1404-x86_64', 'ubuntu-1604-x86_64', 'ubuntu-1804-x86_64']
28 images: ['debian-8-x86_64', 'debian-9-x86_64', 'debian-10-x86_64', 'ubuntu-1404-x86_64', 'ubuntu-1604-x86_64', 'ubuntu-1804-x86_64', 'ubuntu-2004-x86_64']