Reland "Remove Python 2 support for PRESUBMIT.py"

This reverts commit d4c6cbeb61.

Reason for revert: Python 2 invocations of the presubmit system
should be gone now.

Original change's description:
> Revert "Remove Python 2 support for PRESUBMIT.py"
>
> This reverts commit 8454fc2458.
>
> Reason for revert: post submit hooks failing
> https://crbug.com/1422416
>
> Original change's description:
> > Remove Python 2 support for PRESUBMIT.py
> >
> > The presubmit system still supports invoking PRESUBMIT.py files using
> > Python 2. This has recently been turned off on the bots so this change
> > removes support more completely.
> >
> > There are still some python3 parameters being passed around - it seemed
> > better to do the simplest possible removal now, with a follow-up change
> > to remove more support code after this has sat for a while.
> >
> > Tests run from PRESUBMIT.py files could still be run using Python 2, but
> > those should also have been addressed already. Removing support for that
> > will be done in a subsequent change.
> >
> > Bug: 1207012
> > Change-Id: Id244d547a04438f83734dba269c3cc180c148b37
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4315183
> > Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
> > Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
>
> Bug: 1207012
> Bug: 1422416
> Change-Id: Iaf3102e63ec3c698d0258fac5746dbd92c30edbb
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4317176
> Auto-Submit: Josip Sokcevic <sokcevic@chromium.org>
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>

Bug: 1207012
Bug: 1422416
Change-Id: I9521095989c708188fca0251fa13881e086b1395
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4516015
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>

git_cl.py

@@ -1432,21 +1432,11 @@ class Changelist(object):
             ' was not specified. To enable ResultDB, please run the command'
             ' again with the --realm argument to specify the LUCI realm.')
 
-    py3_results = self._RunPresubmit(args,
-                                     description,
-                                     use_python3=True,
-                                     resultdb=resultdb,
-                                     realm=realm)
-    if py3_results.get('skipped_presubmits', 1) == 0:
-      print('No more presubmits to run - skipping Python 2 presubmits.')
-      return py3_results
-
-    py2_results = self._RunPresubmit(args,
-                                     description,
-                                     use_python3=False,
-                                     resultdb=resultdb,
-                                     realm=realm)
-    return self._MergePresubmitResults(py2_results, py3_results)
+    return self._RunPresubmit(args,
+                              description,
+                              use_python3=True,
+                              resultdb=resultdb,
+                              realm=realm)
 
   def _RunPresubmit(self,
                     args,

presubmit_support.py

@@ -309,33 +309,6 @@ def prompt_should_continue(prompt_string):
   response = sys.stdin.readline().strip().lower()
   return response in ('y', 'yes')
 
-
-def _ShouldRunPresubmit(script_text, use_python3):
-  """Try to figure out whether these presubmit checks should be run under
-    python2 or python3. We need to do this without actually trying to
-    compile the text, since the text might compile in one but not the
-    other.
-
-    Args:
-      script_text: The text of the presubmit script.
-      use_python3: if true, will use python3 instead of python2 by default
-                if USE_PYTHON3 is not specified.
-
-    Return:
-      A boolean if presubmit should be executed
-  """
-  if os.getenv('LUCI_OMIT_PYTHON2') == 'true':
-    # If LUCI omits python2, run all presubmits with python3, regardless of
-    # USE_PYTHON3 variable.
-    return True
-
-  m = re.search('^USE_PYTHON3 = (True|False)$', script_text, flags=re.MULTILINE)
-  if m:
-    use_python3 = m.group(1) == 'True'
-
-  return ((sys.version_info.major == 2) and not use_python3) or \
-      ((sys.version_info.major == 3) and use_python3)
-
 # Top level object so multiprocessing can pickle
 # Public access through OutputApi object.
 class _PresubmitResult(object):
@@ -1506,14 +1479,9 @@ def DoPostUploadExecuter(change, gerrit_obj, verbose, use_python3=False):
     filename = os.path.abspath(filename)
     # Accept CRLF presubmit script.
     presubmit_script = gclient_utils.FileRead(filename).replace('\r\n', '\n')
-    if _ShouldRunPresubmit(presubmit_script, use_python3):
-      if sys.version_info[0] == 2:
-        sys.stdout.write(
-            'Running %s under Python 2. Add USE_PYTHON3 = True to prevent '
-            'this.\n' % filename)
-      elif verbose:
-        sys.stdout.write('Running %s\n' % filename)
-      results.extend(executer.ExecPresubmitScript(presubmit_script, filename))
+    if verbose:
+      sys.stdout.write('Running %s\n' % filename)
+    results.extend(executer.ExecPresubmitScript(presubmit_script, filename))
 
   if not results:
     return 0
@@ -1787,29 +1755,18 @@ def DoPresubmitChecks(change,
     executer = PresubmitExecuter(change, committing, verbose, gerrit_obj,
                                  dry_run, thread_pool, parallel, use_python3,
                                  no_diffs)
-    skipped_count = 0;
     if default_presubmit:
       if verbose:
         sys.stdout.write('Running default presubmit script.\n')
       fake_path = os.path.join(change.RepositoryRoot(), 'PRESUBMIT.py')
-      if _ShouldRunPresubmit(default_presubmit, use_python3):
-        results += executer.ExecPresubmitScript(default_presubmit, fake_path)
-      else:
-        skipped_count += 1
+      results += executer.ExecPresubmitScript(default_presubmit, fake_path)
     for filename in presubmit_files:
       filename = os.path.abspath(filename)
       # Accept CRLF presubmit script.
       presubmit_script = gclient_utils.FileRead(filename).replace('\r\n', '\n')
-      if _ShouldRunPresubmit(presubmit_script, use_python3):
-        if sys.version_info[0] == 2:
-          sys.stdout.write(
-              'Running %s under Python 2. Add USE_PYTHON3 = True to prevent '
-              'this.\n' % filename)
-        elif verbose:
-          sys.stdout.write('Running %s\n' % filename)
-        results += executer.ExecPresubmitScript(presubmit_script, filename)
-      else:
-        skipped_count += 1
+      if verbose:
+        sys.stdout.write('Running %s\n' % filename)
+      results += executer.ExecPresubmitScript(presubmit_script, filename)
 
     results += thread_pool.RunAsync()
 
@@ -1880,7 +1837,6 @@ def DoPresubmitChecks(change,
             for warning in messages.get('Warnings', [])
         ],
         'more_cc': executer.more_cc,
-        'skipped_presubmits': skipped_count,
       }
 
       gclient_utils.FileWrite(

tests/git_cl_test.py

@@ -3706,25 +3706,6 @@ class ChangelistTest(unittest.TestCase):
         '--json_output', '/tmp/fake-temp2',
         '--description_file', '/tmp/fake-temp1',
     ])
-    subprocess2.Popen.assert_any_call([
-        'vpython', 'PRESUBMIT_SUPPORT',
-        '--root', 'root',
-        '--upstream', 'upstream',
-        '--verbose', '--verbose',
-        '--gerrit_url', 'https://chromium-review.googlesource.com',
-        '--gerrit_project', 'project',
-        '--gerrit_branch', 'refs/heads/main',
-        '--author', 'author',
-        '--issue', '123456',
-        '--patchset', '7',
-        '--commit',
-        '--may_prompt',
-        '--parallel',
-        '--all_files',
-        '--no_diffs',
-        '--json_output', '/tmp/fake-temp4',
-        '--description_file', '/tmp/fake-temp3',
-    ])
     gclient_utils.FileWrite.assert_any_call(
         '/tmp/fake-temp1', 'description')
     metrics.collector.add_repeated('sub_commands', {

tests/presubmit_unittest.py

@@ -664,11 +664,6 @@ class PresubmitUnittest(PresubmitTestsBase):
             change=change, gerrit_obj=None, verbose=False))
     expected = (r'Running Python ' + str(sys.version_info.major) +
                 r' post upload checks \.\.\.\n')
-    if sys.version_info[0] == 2:
-      expected += ('Running .*PRESUBMIT.py under Python 2. Add USE_PYTHON3 = '
-                   'True to prevent this.\n')
-      expected += ('Running .*PRESUBMIT.py under Python 2. Add USE_PYTHON3 = '
-                   'True to prevent this.\n')
     self.assertRegexpMatches(sys.stdout.getvalue(), expected)
 
   def testDoPostUploadExecuterWarning(self):
@@ -700,17 +695,12 @@ class PresubmitUnittest(PresubmitTestsBase):
         presubmit.DoPostUploadExecuter(
             change=change, gerrit_obj=None, verbose=False))
 
-    extra = ''
-    if sys.version_info[0] == 2:
-      extra = ('Running .*PRESUBMIT.py under Python 2. Add USE_PYTHON3 = True '
-               'to prevent this.\n')
     expected = ('Running Python ' + str(sys.version_info.major) + ' '
                 'post upload checks \.\.\.\n'
-                '%s'
                 '\n'
                 '\*\* Post Upload Hook Messages \*\*\n'
                 '!!\n'
-                '\n' % extra)
+                '\n')
     self.assertRegexpMatches(sys.stdout.getvalue(), expected)
 
   def testDoPresubmitChecksNoWarningsOrErrors(self):
@@ -806,7 +796,6 @@ def CheckChangeOnCommit(input_api, output_api):
           }
         ],
         'more_cc': ['me@example.com'],
-        'skipped_presubmits': 0,
     }
 
     fake_result_json = json.dumps(fake_result, sort_keys=True)