At first glance it looks like some feature is not being detected/enabled during the python2.7 build. From https://buildd.debian.org/status/fetch.php?pkg=python2.7&arch=kfreebsd-amd64&ver=2.7.4-2&stamp=1365768399 :checking for sem_open... yes checking for sem_timedwait... yes checking for sem_getvalue... yes checking for sem_unlink... yes[...]checking whether POSIX semaphores are enabled... no
Not really. We do not support "named semaphores" (sem_open), but we do support (unnamed semaphores) (sem_init). The "named only" functions returns ENOSYS. Petr