emerge skencil failed for me with a "setup.py configure failed" message. On a line above I saw that the file setup.py couldn't be found. I looked for the file, and found it in /var/tmp/portage/skencil-0.6.15/work/sketch-0.6.15/ Emerge found it and installed the program when I changed the S variable in the ebuild to S=${WORKDIR}/sketch-0.6.15/
0.6.16_pre3 (which is REALLY called skencil) is now stable and works.