All relevant ports should be converted to the new USES=python syntax. review D1416 contains an update to the *.mk files to remove the compatibility bits.
Take for exp-run
A commit references this bug: Author: antoine Date: Tue Jan 6 13:59:36 UTC 2015 New revision: 376425 URL: https://svnweb.freebsd.org/changeset/ports/376425 Log: Do not override USES set by slave ports in master ports PR: 196477 Changes: head/net/miniupnpc/Makefile head/net-p2p/libtorrent-rasterbar/Makefile
Exp-run results with patch committed in r376425: http://package23.nyi.freebsd.org/build.html?mastername=93amd64-default-D1416&build=2015-01-05_08h29m30s http://package18.nyi.freebsd.org/build.html?mastername=101amd64-default-D1416&build=2015-01-05_08h30m20s 0 new failure, looks good.