Make fix_encoding_test py3 compatible

And run it in presubmit checks

R=gavinmak@google.com

Change-Id: If2a8848f6ce85c466f45d9bf0f4fca6b4d75312f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3296677
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

PRESUBMIT.py

@@ -109,7 +109,6 @@ def CheckUnitTestsOnCommit(input_api, output_api):
         r'.*recipes_test\.py$',
     ])
   py2_only_tests = [
-      'fix_encoding_test.py',
       'recipes_test.py',
   ]
 

tests/fix_encoding_test.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # coding=utf-8
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -23,8 +23,8 @@ class FixEncodingTest(unittest.TestCase):
 
   def test_code_page(self):
     # Make sure printing garbage won't throw.
-    print(self.text.encode() + '\xff')
-    print(self.text.encode() + '\xff', file=sys.stderr)
+    print(self.text.encode() + b'\xff')
+    print(self.text.encode() + b'\xff', file=sys.stderr)
 
   def test_utf8(self):
     # Make sure printing utf-8 works.
@@ -58,5 +58,5 @@ class FixEncodingTest(unittest.TestCase):
 
 
 if __name__ == '__main__':
-  assert fix_encoding.fix_encoding()
+  fix_encoding.fix_encoding()
   unittest.main()