toolchain-utils: Partially port scripts to python 3

This patch ports some still-in-use python scripts under root directory
of toolchain-utils to python 3.

BUG=chromium:1011676
TEST=Passed unittests and tested with manually launching.

Change-Id: Id6066944780a7204fe4746cd271f41ac20f2274d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2049103
Commit-Queue: Zhizhou Yang <zhizhouy@google.com>
Tested-by: Zhizhou Yang <zhizhouy@google.com>
Auto-Submit: Zhizhou Yang <zhizhouy@google.com>
Reviewed-by: George Burgess <gbiv@chromium.org>
diff --git a/remote_test.py b/remote_test.py
index 62598d5..98ff62a 100755
--- a/remote_test.py
+++ b/remote_test.py
@@ -1,6 +1,10 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
 #
-# Copyright 2010 Google Inc. All Rights Reserved.
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
 """Script to wrap test_that script.
 
 This script can login to the chromeos machine using the test private key.