awesome-3.0_rc4 now needs dev-libs/luafilesystem as a runtime dependency. See the post and thread at http://article.gmane.org/gmane.comp.window-managers.awesome/2807 for some related discussion.
fixed in cvs. thanks. btw, luafilesystem will be removed from RDEPEND in next release. http://git.naquadah.org/?p=awesome.git;a=commit;h=fdddc839e83b79e75b202eb01478268fef63fe0a