Your package rubygem-haml failed to build from source in current F28. https://koji.fedoraproject.org/koji/taskinfo?taskID=24890405 For details on mass rebuild see https://fedoraproject.org/wiki/Fedora_28_Mass_Rebuild
rubygem-haml-5.0.4-1.fc28 has been submitted as an update to Fedora 28. https://bodhi.fedoraproject.org/updates/FEDORA-2018-589db01288
rubygem-haml-5.0.4-1.fc28 has been pushed to the Fedora 28 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-589db01288
rubygem-haml-5.0.4-1.fc28 has been pushed to the Fedora 28 stable repository. If problems still persist, please make note of it in this bug report.