daemon: Used the communicate() method to interact with subprocesses.

daemon/core/phys/pnodes.py

@@ -90,14 +90,10 @@ class PhysicalNode(PyCoreNode):
         '''
         os.chdir(self.nodedir)
         # in Python 2.7 we can use subprocess.check_output() here
-        tmp = subprocess.Popen(args, stdin = subprocess.PIPE,
+        tmp = subprocess.Popen(args, stdin = open(os.devnull, 'r'),
                                stdout = subprocess.PIPE,
-                               stderr = subprocess.PIPE)
-        result = tmp.stdout.read()
-        result += tmp.stderr.read()
-        tmp.stdin.close()
-        tmp.stdout.close()
-        tmp.stderr.close()
+                               stderr = subprocess.STDOUT)
+        result, err = tmp.communicate() # err will always be None
         status = tmp.wait()
         return (status, result)