ACCEPT_KEYWORDS="~x86" emerge -uDavt world 

These are the packages that would be merged, in reverse order:

Calculating world dependencies -[nomerge      ] app-office/lyx-1.5.1 [1.4.2] USE="-tetex%" LINGUAS="-he%" 
[nomerge      ]  net-print/cups-1.2.12-r1 [1.2.10-r1] 
[nomerge      ]   net-print/hplip-2.7.9-r1 [1.7.4a-r1] USE="-doc% -minimal%" 
[nomerge      ]    dev-python/PyQt-3.17.3  USE="-debug -doc -examples" 
[ebuild  N    ]     dev-python/qscintilla-2.1  USE="python -debug -doc -examples -qt4" 
[ebuild  N    ]      dev-python/PyQt-3.17.3  USE="-debug -doc -examples" 
!!! Error: circular dependencies:

('ebuild', '/', 'dev-python/PyQt-3.17.3', 'merge') depends on
   ('ebuild', '/', 'dev-python/qscintilla-2.1', 'merge') (hard)
('ebuild', '/', 'dev-python/qscintilla-2.1', 'merge') depends on
   ('ebuild', '/', 'dev-python/PyQt-3.17.3', 'merge') (medium)

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