sys-libs/libcap-ng-0.6.3 was released on 2010-03-11.
sys-libs/libcap-ng-0.6.4 was released on 2010-05-06.
Created attachment 246039 [details, diff] libcap-ng-0.6.4.ebuild.patch
Created attachment 246042 [details, diff] libcap-ng-0.6.4-python.patch
Created attachment 246044 [details, diff] libcap-ng-0.6.4-fix_tests_building.patch
I will fix this bug, if you don't object in 1 week.
Fixed.