Для openSUSE Tumbleweed запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:inescid:grid/openSUSE_Tumbleweed/home:inescid:grid.repo
zypper refresh
zypper install python-rfc3339-validator
Для 15.6 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:inescid:grid/15.6/home:inescid:grid.repo
zypper refresh
zypper install python-rfc3339-validator
Для 15.5 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:inescid:grid/15.5/home:inescid:grid.repo
zypper refresh
zypper install python-rfc3339-validator