Following a post-Project Unfork world update, portage is recommending a preserved-rebuild.
!!! existing preserved libs: >>> package: dev-libs/boost-1.57.0 * - /usr/lib64/libboost_locale.so.1.56.0 * used by /usr/bin/blender (media-gfx/blender-2.72b-r3) * - /usr/lib64/libboost_thread.so.1.56.0 * - /usr/lib64/libboost_chrono.so.1.56.0 * - /usr/lib64/libboost_system.so.1.56.0 Use emerge @preserved-rebuild to rebuild packages using these libraries
There is a dev-python/numpy:0 conflict...
emerge -av @preserved-rebuild
These are the packages that would be merged, in order: Calculating dependencies... done! [ebuild U ] dev-python/requests-2.8.0-r1::gentoo [2.6.0-r1000::gentoo] USE="{-test}" PYTHON_ABIS="(-2.6%) (-2.7%*) (-2.7-jython%) (-2.7-pypy%) (-3.1%) (-3.2%) (-3.2-pypy%) (-3.3%*) (-3.4%*) (-3.5%)" PYTHON_TARGETS="python2_7%* python3_3%* python3_4%* -pypy% -pypy3% -python3_5%" 0 KiB [ebuild U ] dev-python/numpy-1.10.0_p2-r1::gentoo [1.9.2-r1000::gentoo] USE="lapack -doc {-test}" PYTHON_ABIS="(-2.6%) (-2.7%*) (-3.1%) (-3.2%) (-3.3%*) (-3.4%*) (-3.5%)" PYTHON_TARGETS="python2_7%* python3_3%* python3_4%* -python3_5%" 0 KiB [ebuild R ] media-gfx/blender-2.72b-r3::gentoo USE="boost bullet dds elbeem ffmpeg fftw game-engine jack jpeg2k nls openal openexr openmp opennl sdl sndfile tiff -collada -colorio -cycles -debug -doc (-libav) -ndof -openimageio -player -redcode" CPU_FLAGS_X86="sse sse2" PYTHON_TARGETS="python3_4" 0 KiB Total: 3 packages (2 upgrades, 1 reinstall), Size of downloads: 0 KiB !!! Multiple package instances within a single package slot have been pulled !!! into the dependency graph, resulting in a slot conflict: dev-python/numpy:0 (dev-python/numpy-1.10.0_p2-r1:0/0::gentoo, ebuild scheduled for merge) pulled in by dev-python/numpy[python_targets_python3_4(-)?,-python_single_target_jython2_5(-),-python_single_target_jython2_7(-),-python_single_target_pypy(-),-python_single_target_pypy3(-),-python_single_target_python3_3(-),-python_single_target_python3_5(-),-python_single_target_python2_7(-),python_single_target_python3_4(+)] required by (media-gfx/blender-2.72b-r3:0/0::gentoo, ebuild scheduled for merge) dev-python/numpy[python_targets_python2_7(-)?,-python_single_target_jython2_5(-),-python_single_target_jython2_7(-),-python_single_target_pypy(-),-python_single_target_pypy3(-),-python_single_target_python3_3(-),-python_single_target_python3_4(-),-python_single_target_python3_5(-),python_single_target_python2_7(+)] required by (media-libs/opencv-2.4.10:0/2.4::gentoo, installed) dev-python/numpy[python_targets_python2_7(-)?,-python_single_target_jython2_5(-),-python_single_target_jython2_7(-),-python_single_target_pypy(-),-python_single_target_pypy3(-),-python_single_target_python3_3(-),-python_single_target_python3_4(-),-python_single_target_python3_5(-),python_single_target_python2_7(+)] required by (media-gfx/inkscape-0.91:0/0::gentoo, installed) dev-python/numpy[python_targets_python2_7(-)?,-python_single_target_python2_7(-)] required by (media-libs/aubio-0.4.1:0/0::gentoo, installed) (dev-python/numpy-1.9.2-r1000:0/0::gentoo, installed) pulled in by dev-python/numpy[python_abis_2.7] required by (dev-python/pygtk-2.24.0-r1000:2/2::gentoo, installed) ^^^^^^^^^^^^^^^ It may be possible to solve this problem by using package.mask to prevent one of those packages from being selected. However, it is also possible that conflicting dependencies exist such that they are impossible to satisfy simultaneously. If such a conflict exists in the dependencies of two different packages, then those packages can not be installed simultaneously. You may want to try a larger value of the --backtrack option, such as --backtrack=30, in order to see if that will solve this conflict automatically. For more information, see MASKED PACKAGES section in the emerge man page or refer to the Gentoo Handbook.