wait for pid ends; correct error handling

sleeper.py

import os
import time
import sys
from subprocess import call

def check_pid(pid):        
    """ Check For the existence of a unix pid. """
    while True:
        try:
            os.kill(pid, 0)
        except OSError:
            # pid is not running
            print('Proc done')
            call('/usr/sbin/pm-hibernate')
            os._exit(0)
        else:
            print('wait for it')
            time.sleep(5)

if __name__ == '__main__':
    check_pid(int(sys.argv[1]))
# ===============================================================
import os

def pid_exists(pid): 
    if pid < 0: return False #NOTE: pid == 0 returns True
    try:
        os.kill(pid, 0) 
    except ProcessLookupError: # errno.ESRCH
        return False # No such process
    except PermissionError: # errno.EPERM
        return True # Operation not permitted (i.e., process exists)
    else:
        return True # no error, we can send a signal to the process