I have python3.6 installed but I have a problem with eselect-python and other parts of my gentoo installation being able to see and use it. Reinstalling python3.6 by executing emerge from /usr/lib/python-exec/python3.6/emerge is successful, but it is still not found by either or any component.
Support for python3_6 TARGETS is being removed from Gentoo and currently masked. The interpreter itself will stay for as long as possible, but will not be recognized by portage, python-exec, or eselect-python. If you really still need to use it, may want to consider virtualenv and similar solutions. https://archives.gentoo.org/gentoo-dev/message/a321277c250ee1a5853ebc2e0dda5a6e
Actually, I feel my answer needs review. Unsure if masking for python-exec as well was intended (seeing how python2_7 isn't), so assigning this to python-exec just in case.
Yes, that's intended. If you want to use 3.6 for the next week, you need to unmask it. 2.7 wasn't masked because it was incrementally removed from all packages, so there was no need for a final mask. 3.6 is removed with a single cutoff date, so it is more practical to provide a mask while the last packages are last rited.