Something

livecd / # emerge ati-drivers
Calculating dependencies... done!
[nomerge      ] dev-python/pycrypto-2.0.1-r5  USE="-bindist -gmp -test" 
[nomerge      ]  dev-lang/python-2.4.4-r4  USE="berkdb gdbm ipv6 ncurses readline ssl -bootstrap -build -doc -examples -nocxx -nothreads -tk -ucs2" 
[nomerge      ]   app-admin/python-updater-0.2  
[nomerge      ]    sys-apps/portage-2.1.2.7  USE="-build -doc -epydoc (-selinux)" LINGUAS="-pl" 
[nomerge      ]     app-shells/bash-3.2_p15-r1  USE="nls -afs -bashlogger -vanilla" 
[nomerge      ]      sys-libs/ncurses-5.6  USE="gpm unicode -bootstrap -build -debug -doc -minimal -nocxx -trace" 
[ebuild  N    ]       sys-libs/gpm-1.20.1-r5  USE="(-selinux)" 
[ebuild  N    ]        sys-libs/ncurses-5.6  USE="gpm unicode -bootstrap -build -debug -doc -minimal -nocxx -trace" 
!!! Error: circular dependencies:

('ebuild', '/', 'sys-libs/ncurses-5.6', 'merge') depends on
   ('ebuild', '/', 'sys-libs/gpm-1.20.1-r5', 'merge') (hard)
('ebuild', '/', 'sys-libs/gpm-1.20.1-r5', 'merge') depends on
   ('ebuild', '/', 'sys-libs/ncurses-5.6', 'merge') (hard)

!!! Note that circular dependencies can often be avoided by temporarily
!!! disabling USE flags that trigger optional dependencies.