rubygem-w3c_validators from home:mschnitzer project
Select Your Operating System
Add repository and install manually
For openSUSE Leap 15.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:mschnitzer/openSUSE_Leap_15.2/home:mschnitzer.repo zypper refresh zypper install rubygem-w3c_validators