CodeHealth: Python3 migration for tools_webrtc/mb/

This CL includes:
* set Pylint to 2.7 in tools_webrtc/mb/PRESUBMIT.py
* fix some style warnings caused by scripts in tools_webrtc/mb/
* pass skip_shebang_check=True within tools_webrtc/mb/PRESUBMIT.py

Bug: chromium:1262287, chromium:1262352
Change-Id: Iae4f111942d724db6a7f4585c97a7c26c1e6ccc0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/239660
Commit-Queue: Nidhi Jaju <nidhijaju@chromium.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35477}

tools_webrtc/mb/PRESUBMIT.py

@@ -11,12 +11,28 @@ def _CommonChecks(input_api, output_api):
   results = []
 
   # Run Pylint over the files in the directory.
-  pylint_checks = input_api.canned_checks.GetPylint(input_api, output_api)
+  pylint_checks = input_api.canned_checks.GetPylint(
+      input_api,
+      output_api,
+      version='2.7',
+      # Disabling certain python3-specific warnings until the conversion
+      # is complete.
+      disabled_warnings=[
+          'super-with-arguments',
+          'raise-missing-from',
+          'useless-object-inheritance',
+          'arguments-differ',
+      ],
+  )
   results.extend(input_api.RunTests(pylint_checks))
 
   # Run the MB unittests.
   results.extend(input_api.canned_checks.RunUnitTestsInDirectory(
-      input_api, output_api, '.', [ r'^.+_unittest\.py$']))
+      input_api,
+      output_api,
+      '.',
+      [ r'^.+_unittest\.py$'],
+      skip_shebang_check=True))
 
   # Validate the format of the mb_config.pyl file.
   cmd = [input_api.python_executable, 'mb.py', 'validate']

tools_webrtc/mb/mb.py

@@ -28,7 +28,10 @@ import sys
 import subprocess
 import tempfile
 import traceback
-import urllib2
+try:
+  from urllib2 import urlopen # for Python2
+except ImportError:
+  from urllib.request import urlopen # for Python3
 
 from collections import OrderedDict
 
@@ -330,7 +333,6 @@ class MetaBuildWrapper(object):
         if self.args.swarmed:
             cmd, _ = self.GetSwarmingCommand(self.args.target[0], vals)
             return self._RunUnderSwarming(build_dir, target, cmd)
-        else:
         return self._RunLocallyIsolated(build_dir, target)
 
     def _RunUnderSwarming(self, build_dir, target, isolate_cmd):
@@ -1222,7 +1224,7 @@ class MetaBuildWrapper(object):
 
     def Fetch(self, url):
         # This function largely exists so it can be overridden for testing.
-        f = urllib2.urlopen(url)
+        f = urlopen(url)
         contents = f.read()
         f.close()
         return contents
@@ -1230,7 +1232,7 @@ class MetaBuildWrapper(object):
     def MaybeMakeDirectory(self, path):
         try:
             os.makedirs(path)
-        except OSError, e:
+        except OSError as e:
             if e.errno != errno.EEXIST:
                 raise
 

tools_webrtc/mb/mb_unittest.py

@@ -11,7 +11,10 @@
 
 import ast
 import json
-import StringIO
+try:
+  from StringIO import StringIO # for Python2
+except ImportError:
+  from io import StringIO # for Python3
 import os
 import re
 import sys
@@ -96,7 +99,7 @@ class FakeMBW(mb.MetaBuildWrapper):
     self.dirs.add(tmp_dir)
     return tmp_dir
 
-  def TempFile(self, mode='w'):
+  def TempFile(self):
     return FakeFile(self.files)
 
   def RemoveFile(self, path):
@@ -116,7 +119,6 @@ class FakeMBW(mb.MetaBuildWrapper):
       path = self.PathJoin(self.cwd, path)
     if self.sep == '\\':
       return re.sub(r'\\+', r'\\', path)
-    else:
     return re.sub('/+', '/', path)
 
 
@@ -859,7 +861,7 @@ class UnitTest(unittest.TestCase):
   def test_help(self):
     orig_stdout = sys.stdout
     try:
-      sys.stdout = StringIO.StringIO()
+      sys.stdout = StringIO()
       self.assertRaises(SystemExit, self.check, ['-h'])
       self.assertRaises(SystemExit, self.check, ['help'])
       self.assertRaises(SystemExit, self.check, ['help', 'gen'])