root/pypi: links for ubuntu-iso-download

root/pypi ubuntu-iso-download-21.1.tar.gz
root/pypi ubuntu-iso-download-20.1.tar.gz
root/pypi ubuntu-iso-download-19.2.tar.gz
root/pypi ubuntu-iso-download-19.1.tar.gz
root/pypi ubuntu-iso-download-18.3.tar.gz
root/pypi ubuntu-iso-download-18.2.tar.gz
root/pypi ubuntu-iso-download-18.1.tar.gz
root/pypi ubuntu-iso-download-18.0.tar.gz