worker: restore old countcpus code (issue4869)...
worker: restore old countcpus code (issue4869)
This is a backout of d29859cfcfc2. The stdlib implementation of
multiprocessing.cpu_count() attempts to invoke a process on BSD and
Darwin platforms (at least on 2.7). Under certain conditions (such as
cwd being removed) this could raise. Our old code was silently catching
the exception.
The old code was more robust, so restore it.