> sys.platform refers to build time information,
> so the platform module won't help.

When I wrote my patch, I realized that sys.platform is used to get the runtime information, which is wrong. See the tests in Lib/test/test_*.py: they use sys.platform to check features of the running OS (kernel). It is mostly to test FreeBSD major version, and it looks like Python is build on the same FreeBSD major version that it is running on. Maybe because on FreeBSD, most programs are compiled instead of using prebuild packages (pkgadd).