Comment # 3 on bug 1170990 from Michael Andres

It's computed by the solver and depends in the packages dependencies and the
systems settings. 

@Yunhe Guo: Please provide a solver testcase. AFAIK `YaST > Software
Management` provides a button to create a testcase in it's menues. After this,
collect and attach the yast logs.
(see https://en.opensuse.org/openSUSE:Report_a_YaST_bug)