Your package rubygem-rack-mount failed to build from source in current rawhide. http://koji.fedoraproject.org/koji/taskinfo?taskID=10151276 For details on mass rebuild see https://fedoraproject.org/wiki/Fedora_23_Mass_Rebuild
Created attachment 1048144 [details] build.log
Created attachment 1048145 [details] root.log
Created attachment 1048146 [details] state.log
This bug appears to have been reported against 'rawhide' during the Fedora 23 development cycle. Changing version to '23'. (As we did not run this process for some time, it could affect also pre-Fedora 23 development cycle bugs. We are very sorry. It will help us with cleanup during Fedora 23 End Of Life. Thank you.) More information and reason for this action is here: https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora23
rubygem-rack-mount was retired for F23+. No reason to fix this.