Для Goupilmtos15.6 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:goupilmtos:devel:languages:python/Goupilmtos15.6/home:goupilmtos:devel:languages:python.repo
zypper refresh
zypper install python-diff-match-patch
Для Goupilmtos15.5 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:goupilmtos:devel:languages:python/Goupilmtos15.5/home:goupilmtos:devel:languages:python.repo
zypper refresh
zypper install python-diff-match-patch