Revert "[CodeHealth] Migrate multiple presubmit checks from Python2 to Python3"

This reverts commit cac5f385cd374193bc8e0f1bc5a90144f1d4ed3a.

Reason for revert: It looks like not all the bots are running python3, which is causing some of these scripts to fail.

Original change's description:
> [CodeHealth] Migrate multiple presubmit checks from Python2 to Python3
>
> and fixed resulting errors.
>
> Bug: 1223892
> Change-Id: I9a4c27d845e2f87cd0a609953f5ed4bfe4b6cef0
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3234222
> Reviewed-by: Kenneth Russell <[email protected]>
> Reviewed-by: Brian Sheedy <[email protected]>
> Reviewed-by: Dirk Pranke <[email protected]>
> Commit-Queue: Joshua Hood <[email protected]>
> Cr-Commit-Position: refs/heads/main@{#956234}

Bug: 1223892
Change-Id: I0c72741f367dada16ccfd23ed678ca127023ac42
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3373208
Owners-Override: Devlin Cronin <[email protected]>
Reviewed-by: Brian Sheedy <[email protected]>
Bot-Commit: Rubber Stamper <[email protected]>
Commit-Queue: Devlin Cronin <[email protected]>
Cr-Commit-Position: refs/heads/main@{#956742}
diff --git a/testing/merge_scripts/standard_gtest_merge_test.py b/testing/merge_scripts/standard_gtest_merge_test.py
index 42d37f2..2de820c4 100755
--- a/testing/merge_scripts/standard_gtest_merge_test.py
+++ b/testing/merge_scripts/standard_gtest_merge_test.py
@@ -3,7 +3,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import io
+import cStringIO
 import json
 import logging
 import os
@@ -429,7 +429,7 @@
   """Tests for merge_shard_results function."""
 
   def setUp(self):
-    super().setUp()
+    super(MergeShardResultsTest, self).setUp()
     self.summary = None
     self.test_files = []
 
@@ -440,7 +440,7 @@
       self.test_files.append(abs_path)
 
   def call(self):
-    stdout = io.StringIO()
+    stdout = cStringIO.StringIO()
     with mock.patch('sys.stdout', stdout):
       merged = standard_gtest_merge.merge_shard_results(
           self.summary, self.test_files)
@@ -601,7 +601,7 @@
 class CommandLineTest(common_merge_script_tests.CommandLineTest):
 
   def __init__(self, methodName='runTest'):
-    super().__init__(methodName, standard_gtest_merge)
+    super(CommandLineTest, self).__init__(methodName, standard_gtest_merge)
 
 
 if __name__ == '__main__':