Your package libkolab failed to build from source in current F28. https://koji.fedoraproject.org/koji/taskinfo?taskID=24812456 For details on mass rebuild see https://fedoraproject.org/wiki/Fedora_28_Mass_Rebuild
It fails because it's looking for what looks like a kdelibs4 header: In file included from /builddir/build/BUILD/libkolab-1.0.2/kolabformat/v2helpers.h:23, from /builddir/build/BUILD/libkolab-1.0.2/kolabformat/kolabobject.cpp:20: /builddir/build/BUILD/libkolab-1.0.2/./kolabformatV2/kolabbase.h:40:10: fatal error: kdatetime.h: No such file or directory #include <kdatetime.h> ^~~~~~~~~~~~~ I tried just adding a BR for kf5-kdelibs4support-devel , but that doesn't help (as it doesn't include the right dir on the include path). Before going any further in trying to fix this, should the package just be retired for F28+ ? It doesn't seem to be needed: the only thing that depends on anything provided by libkolab is python2-kolab, and nothing requires anything that python2-kolab provides. AFAICS.
That's a deprecated (and recently removed) api from kf5-kcalendarcore I believe
My recommendation is to retire this, at least until it's fixed and/or anything else really needs it.
See also further correspondence in bug #1518800 (marking as dup, since there's more info there) *** This bug has been marked as a duplicate of bug 1518800 ***