For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jloehel:python/openSUSE_Tumbleweed/home:jloehel:python.repo
zypper refresh
zypper install python-xml2rfc
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jloehel:python/15.6/home:jloehel:python.repo
zypper refresh
zypper install python-xml2rfc
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jloehel:python/15.5/home:jloehel:python.repo
zypper refresh
zypper install python-xml2rfc
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jloehel:python/15.4/home:jloehel:python.repo
zypper refresh
zypper install python-xml2rfc