Linux can mask legitimate ENOENT exceptions as NoSuchProcess

[giampaolo]

Under Linux wrap_exception decorator indiscriminately treats ENOENT as an alias for NSP:

psutil/psutil/_pslinux.py

Line 1339 in dd5ce9c

if err.errno in (errno.ENOENT, errno.ESRCH):

This may not always be true. For instance, if we open() a file under /proc which does not exist because the Linux kernel does not support that particular proc file we'll erroneously think the process does not exist.
Instead we want to see the original ENOENT exception.