warden_filer: compatibility with Python3

warden_filer/warden_filer.py

-#!/usr/bin/python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 #
 # Copyright (C) 2011-2015 Cesnet z.s.p.o
@@ -18,7 +18,13 @@ import resource
 import atexit
 import argparse
 from os import path, mkdir
-from random import choice, randint;
+from random import choice, randint
+
+# for py2/py3 compatibility
+try:
+    basestring
+except NameError:
+    basestring = str
 
 VERSION = "3.0-beta2"
 
@@ -392,7 +398,7 @@ def daemonize(
     # PID file
     if pidfile is not None:
         pidd = os.open(pidfile, os.O_RDWR|os.O_CREAT|os.O_EXCL|os.O_TRUNC)
-        os.write(pidd, str(os.getpid())+"\n")
+        os.write(pidd, (str(os.getpid())+"\n").encode())
         os.close(pidd)
         # Define and setup atexit closure
         @atexit.register