rubygem-rack-test from openSUSE:infrastructure:redmine:stage project

需要 15.6 ，用 root 執行：

zypper addrepo https://download.opensuse.org/repositories/openSUSE:infrastructure:redmine:stage/15.6/openSUSE:infrastructure:redmine:stage.repo
zypper refresh
zypper install rubygem-rack-test