Too wide permissions for /tmp/luigi

Luigi calls chmod with 0o777 for pid_dir and pid files which is very bad for security reasons.

In my opinion the proper use case for the locking mechanism should be: a) set different lock_pid_dir config option for different users b) make all worker processes run in the same unix group to enable sharing the same pid_dir

So I recommend changing permissions to 770 for dir and 660 for pid files (or at most 775/664).