Revert "[CodeHealth] Migrate remainder of testing/ to Python3 compatible syntax"

This reverts commit 8defc6c6da91e4b7d7a686b7bb67658d9a5ebe55.

Reason for revert: Makes win-chrome fail:
https://ci.chromium.org/p/chrome/builders/try/win-chrome/4538

Original change's description:
> [CodeHealth] Migrate remainder of testing/ to Python3 compatible syntax
>
> and Pylint2.7, and fix resulting errors.
>
> Bug: 1262363
> Change-Id: I09628427dd4caf9d873f3b489b897054430f8567
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3557490
> Reviewed-by: Ben Pastene <[email protected]>
> Commit-Queue: Joshua Hood <[email protected]>
> Cr-Commit-Position: refs/heads/main@{#996200}

Bug: 1262363
Change-Id: I74384a8cbd77e0db5adbbd5815d54e836472b756
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3607233
Auto-Submit: Sebastien Lalancette <[email protected]>
Reviewed-by: Ben Pastene <[email protected]>
Commit-Queue: Ben Pastene <[email protected]>
Cr-Commit-Position: refs/heads/main@{#996362}
diff --git a/testing/PRESUBMIT.py b/testing/PRESUBMIT.py
index 6a5524c..61b4fc1 100644
--- a/testing/PRESUBMIT.py
+++ b/testing/PRESUBMIT.py
@@ -23,9 +23,7 @@
       input_api,
       output_api,
       '.',
-      [r'^.+_unittest\.py$'],
-      run_on_python3=USE_PYTHON3,
-      skip_shebang_check=True))
+      [r'^.+_unittest\.py$']))
   output.extend(input_api.canned_checks.RunUnitTestsInDirectory(
       input_api,
       output_api,
@@ -38,6 +36,21 @@
   output.extend(input_api.canned_checks.RunPylint(
       input_api,
       output_api,
+      files_to_skip=[r'gmock.*', r'gtest.*',
+          r'buildbot.*', r'merge_scripts.*', r'trigger_scripts.*',
+          r'unexpected_passes_common.*',
+          r'clusterfuzz.*',
+          r'libfuzzer.*']))
+  # Pylint2.7 is run on subdirs whose presubmit checks are migrated to Python3
+  output.extend(input_api.canned_checks.RunPylint(
+      input_api,
+      output_api,
+      files_to_check=[r'buildbot.*\.py$',
+          r'merge_scripts.*\.py$',
+          r'trigger_scripts.*\.py$',
+          r'unexpected_passes_common.*\.py$',
+          r'clusterfuzz.*\.py$',
+          r'libfuzzer.*\.py$'],
       version='2.7'))
 
   return output