chris@chatcannon:~$ emerge -puDv --newuse --with-bdeps=y world

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

Calculating dependencies... done!

emerge: there are no ebuilds to satisfy ">=dev-python/python-dateutil-2.3[python_targets_python2_7(-)?,python_targets_python3_3(-)?,python_targets_python3_4(-)?,-python_single_target_python2_7(-),-python_single_target_python3_3(-),-python_single_target_python3_4(-)]".
(dependency required by "dev-python/pandas-0.15.1" [ebuild])
(dependency required by "@selected" [set])
(dependency required by "@world" [argument])