For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ykoba:Current_Leap/15.6/home:ykoba:Current_Leap.repo
zypper refresh
zypper install python2-pycairo
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ykoba:Current_Leap/15.5/home:ykoba:Current_Leap.repo
zypper refresh
zypper install python2-pycairo
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ykoba:Current_Leap/15.4/home:ykoba:Current_Leap.repo
zypper refresh
zypper install python2-pycairo