jsonschema >= 4.18.* broken on RHEL6
Broken pipeline: https://gitlab.com/cki-project/pipeline-definition/-/jobs/4612886457
jsonschema >= 4.18 requires rpds-py which requires rust. The prebuild wheels provide manylinux_2_17_x86_64 while RHEL6 only supports manylinux_2_12_x86_64 (pip debug --verbose).