x2t: use with block for open file

(cherry picked from commit e006854)

cloudooo/handler/x2t/handler.py

@@ -116,8 +116,7 @@ class Handler(object):
       os.mkdir(output_dir)
       output_file_name = os.path.join(output_dir, "body.txt")
 
-    config_file = open(config_file_name, "w")
-
+    with open(config_file_name, "w") as config_file:
       config = {
         # 'm_sKey': 'from',
         'm_sFileFrom': input_file_name,
@@ -134,7 +133,6 @@ class Handler(object):
       for key, value in config.items():
         ElementTree.SubElement(root, key).text = value
       ElementTree.ElementTree(root).write(config_file, encoding='utf-8', xml_declaration=True, default_namespace=None, method="xml")
-    config_file.close()
 
     # run convertion binary
     p = Popen(