Reland "Use io.open for opening files"

This is a reland of commit eb16430cf9

Original change's description:
> Use io.open for opening files
>
> Use io.open which is consistent in py2 and py3.
>
> Bug: 1357152
> Change-Id: I49a3df503026bc6918362a9b5600f57111111111
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3872429
> Reviewed-by: Gavin Mak <gavinmak@google.com>
> Commit-Queue: Josip Sokcevic <sokcevic@google.com>

Bug: 1357152
Change-Id: I58881c040ca7333f0247875a0c4abe31cf793b08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3877645
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Auto-Submit: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

presubmit_canned_checks.py

@@ -6,6 +6,7 @@
 
 from __future__ import print_function
 
+import io as _io
 import os as _os
 
 from warnings import warn
@@ -170,9 +171,9 @@ def CheckAuthorizedAuthor(input_api, output_api, bot_allowlist=None):
       input_api.PresubmitLocalPath(), 'AUTHORS')
   author_re = input_api.re.compile(r'[^#]+\s+\<(.+?)\>\s*$')
   valid_authors = []
-  with open(authors_path, 'rb') as fp:
+  with _io.open(authors_path, encoding='utf-8') as fp:
     for line in fp:
-      m = author_re.match(line.decode('utf8'))
+      m = author_re.match(line)
       if m:
         valid_authors.append(m.group(1).lower())
 
@@ -798,7 +799,7 @@ def GetUnitTests(input_api,
   assert run_on_python3 or run_on_python2, (
       'At least one of "run_on_python2" or "run_on_python3" must be set.')
   def has_py3_shebang(test):
-    with open(test) as f:
+    with _io.open(test, encoding='utf-8') as f:
       maybe_shebang = f.readline()
     return maybe_shebang.startswith('#!') and 'python3' in maybe_shebang
 
@@ -1899,7 +1900,7 @@ def CheckJsonParses(input_api, output_api, file_filter=None):
       file_filter=file_filter)
   warnings = []
   for f in affected_files:
-    with open(f.AbsoluteLocalPath()) as j:
+    with _io.open(f.AbsoluteLocalPath(), encoding='utf-8') as j:
       try:
         json.load(j)
       except ValueError:

tests/presubmit_unittest.py

@@ -10,6 +10,7 @@
 from __future__ import unicode_literals
 
 import functools
+import io
 import itertools
 import logging
 import multiprocessing
@@ -26,12 +27,10 @@ if sys.version_info.major == 2:
   from cStringIO import StringIO
   import mock
   import urllib2 as urllib_request
-  BUILTIN_OPEN = '__builtin__.open'
 else:
   from io import StringIO
   from unittest import mock
   import urllib.request as urllib_request
-  BUILTIN_OPEN = 'builtins.open'
 
 _ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 sys.path.insert(0, _ROOT)
@@ -2987,9 +2986,9 @@ the current line as well!
     self.AssertOwnersWorks(approvers=set(['ben@example.com']),
                            is_committing=False)
 
-  @mock.patch(BUILTIN_OPEN, mock.mock_open())
+  @mock.patch('io.open', mock.mock_open())
   def testCannedRunUnitTests(self):
-    open().readline.return_value = ''
+    io.open().readline.return_value = ''
     change = presubmit.Change(
         'foo1', 'description1', self.fake_root_dir, None, 0, 0, None)
     input_api = self.MockInputApi(change, False)
@@ -3033,9 +3032,9 @@ the current line as well!
 
     self.checkstdout('')
 
-  @mock.patch(BUILTIN_OPEN, mock.mock_open())
+  @mock.patch('io.open', mock.mock_open())
   def testCannedRunUnitTestsWithTimer(self):
-    open().readline.return_value = ''
+    io.open().readline.return_value = ''
     change = presubmit.Change(
         'foo1', 'description1', self.fake_root_dir, None, 0, 0, None)
     input_api = self.MockInputApi(change, False)
@@ -3059,9 +3058,9 @@ the current line as well!
 
     self.checkstdout('')
 
-  @mock.patch(BUILTIN_OPEN, mock.mock_open())
+  @mock.patch('io.open', mock.mock_open())
   def testCannedRunUnitTestsWithTimerTimesOut(self):
-    open().readline.return_value = ''
+    io.open().readline.return_value = ''
     change = presubmit.Change(
         'foo1', 'description1', self.fake_root_dir, None, 0, 0, None)
     input_api = self.MockInputApi(change, False)
@@ -3093,9 +3092,9 @@ the current line as well!
         input_api.thread_pool.timeout, mock.ANY)
     timer_instance.start.assert_called_once_with()
 
-  @mock.patch(BUILTIN_OPEN, mock.mock_open())
+  @mock.patch('io.open', mock.mock_open())
   def testCannedRunUnitTestsPython3(self):
-    open().readline.return_value = '#!/usr/bin/env python3'
+    io.open().readline.return_value = '#!/usr/bin/env python3'
     change = presubmit.Change(
         'foo1', 'description1', self.fake_root_dir, None, 0, 0, None)
     input_api = self.MockInputApi(change, False)
@@ -3149,9 +3148,9 @@ the current line as well!
 
     self.checkstdout('')
 
-  @mock.patch(BUILTIN_OPEN, mock.mock_open())
+  @mock.patch('io.open', mock.mock_open())
   def testCannedRunUnitTestsDontRunOnPython2(self):
-    open().readline.return_value = '#!/usr/bin/env python3'
+    io.open().readline.return_value = '#!/usr/bin/env python3'
     change = presubmit.Change(
         'foo1', 'description1', self.fake_root_dir, None, 0, 0, None)
     input_api = self.MockInputApi(change, False)
@@ -3193,9 +3192,9 @@ the current line as well!
 
     self.checkstdout('')
 
-  @mock.patch(BUILTIN_OPEN, mock.mock_open())
+  @mock.patch('io.open', mock.mock_open())
   def testCannedRunUnitTestsDontRunOnPython3(self):
-    open().readline.return_value = '#!/usr/bin/env python3'
+    io.open().readline.return_value = '#!/usr/bin/env python3'
     change = presubmit.Change(
         'foo1', 'description1', self.fake_root_dir, None, 0, 0, None)
     input_api = self.MockInputApi(change, False)