git-rebase-update: Make tests run on Python 3.

Bug: 1009809
Change-Id: I47c9a468b2922248b823ebae5e71863a698c30f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1889166
Reviewed-by: Anthony Polito <apolito@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

tests/git_rebase_update_test.py

@@ -1,10 +1,13 @@
-#!/usr/bin/env python
+#!/usr/bin/env vpython3
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Unit tests for git_rebase_update.py"""
 
+from __future__ import print_function
+from __future__ import unicode_literals
+
 import os
 import sys
 
@@ -24,7 +27,7 @@ class GitRebaseUpdateTest(git_test_utils.GitRepoReadWriteTestBase):
   @classmethod
   def getRepoContent(cls, commit):
     # Every commit X gets a file X with the content X
-    return {commit: {'data': commit}}
+    return {commit: {'data': commit.encode('utf-8')}}
 
   @classmethod
   def setUpClass(cls):
@@ -119,7 +122,7 @@ class GitRebaseUpdateTest(git_test_utils.GitRepoReadWriteTestBase):
     self.assertEqual(self.repo['E'], self.origin['E'])
 
     with self.repo.open('bob', 'wb') as f:
-      f.write('testing auto-freeze/thaw')
+      f.write(b'testing auto-freeze/thaw')
 
     output, _ = self.repo.capture_stdio(self.reup.main)
     self.assertIn('Cannot rebase-update', output)
@@ -158,7 +161,7 @@ class GitRebaseUpdateTest(git_test_utils.GitRepoReadWriteTestBase):
     self.assertIn('sub_K up-to-date', output)
 
     with self.repo.open('bob') as f:
-      self.assertEqual('testing auto-freeze/thaw', f.read())
+      self.assertEqual(b'testing auto-freeze/thaw', f.read())
 
     self.assertEqual(self.repo.git('status', '--porcelain').stdout, '?? bob\n')