Fix directory separtor under Windows.

This patch fix #1332.

testUpdateHostsFile.py

@@ -8,6 +8,7 @@
 import json
 import locale
 import os
+import platform
 import re
 import shutil
 import sys
@@ -62,6 +63,8 @@ class Base(unittest.TestCase):
 
     @property
     def sep(self):
+        if platform.system().lower() == "windows":
+            return "\\"
         return os.sep
 
     def assert_called_once(self, mock_method):