Need to allow `epoll_pwait` in the tor seccomp rules.
Or tor fails to work.
2017/09/10 15:29:20 tor: Sep 10 15:29:20.000 [warn] Warning from libevent: epoll_wait: Function not implemented
2017/09/10 15:29:20 tor: Sep 10 15:29:20.000 [err] libevent call with epoll (with changelist) failed: Function not implemented [38]
2017/09/10 15:29:25 tor: Process has no control port, killing
For what it's worth, this doesn't happen on all systems.