After the default UPSTREAM_DISTRO was changed from debian:stretch to debian:bullseye, the "debian9-repo-install-test" container has gotten built with bullseye instead of stretch. This is the reason for failures of the jenkins job Osmocom-repo-install-debian9 we have seen over the past days.
With this patch applied, it runs through again: https://jenkins.osmocom.org/jenkins/job/Osmocom-repo-install-debian9/339/
