We really shouldn't be pulling in libcalendaring in the first place for the desktop system, but libkolab for centos7 was probably built for the server with libcalendaring support....
---> Package libical.x86_64 0:0.48-6.el7 will be updated
--> Processing Dependency: libical.so.0()(64bit) for package:
libcalendaring-4.9.git.1408631364-2.5.x86_64
--> Processing Dependency: libicalss.so.0()(64bit) for package:
libcalendaring-4.9.git.1408631364-2.5.x86_64
---> Package python-ply.noarch 0:3.4-10.el7 will be installed
--> Finished Dependency Resolution
Error: Package: libcalendaring-4.9.git.1408631364-2.5.x86_64 (installed)
Requires: libical.so.0()(64bit)
Removing: libical-0.48-6.el7.x86_64 (@base/$releasever)
libical.so.0()(64bit)
Updated By: libical-1.0.1-1.el7.x86_64 (base)
~libical.so.1()(64bit)
Error: Package: libcalendaring-4.9.git.1408631364-2.5.x86_64 (installed)
Requires: libicalss.so.0()(64bit)
Removing: libical-0.48-6.el7.x86_64 (@base/$releasever)
libicalss.so.0()(64bit)
Updated By: libical-1.0.1-1.el7.x86_64 (base)
~libicalss.so.1()(64bit)
You could try using --skip-broken to work around the problem