I don't see an error, only lots of warnings. It would seem that the SRPM that you're building is marked as having to be built by the user dominik, who does not exist on your system. To fix the error, try creating a user on your system called dominik.
This shouldn't cause any real problems though; you should still be able to get the RPM file generated that you can then install. Try looking at the
command (depending on your version of RPM)