Reland "git-cl: Fix some python3 compatibility errors."

This is a reland of c87ed606
Fix on the reland: Encode change description before writing to temporary file.

Original change's description:
> git-cl: Fix some python3 compatibility errors.
>
> Also, fix bug in git cl status where the 'updated' field was used to compare messages, even though
> it doesn't exist (see [1]). This CL modifies it to use 'date', which does exist.
>
> [1] https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#change-message-info
>
> Bug: 1002209
> Change-Id: I5a5e1193b8502c3ad35d94808ea178cad7f44ac6
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1891259
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
> Reviewed-by: Anthony Polito <apolito@google.com>

Bug: 1002209
Change-Id: I2f0fc779ea3e361e6d32ee7ce1e53cbddb5cfdea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1898702
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Anthony Polito <apolito@google.com>

git_cl.py

@@ -54,16 +54,13 @@ import subcommand
 import subprocess2
 import watchlists
 
-if sys.version_info.major == 2:
-  import httplib
-  import urllib2 as urllib_request
-  import urllib2 as urllib_error
-  import urlparse
-else:
-  import http.client as httplib
-  import urllib.request as urllib_request
-  import urllib.error as urllib_error
-  import urllib.parse as urlparse
+from third_party import six
+from six.moves import urllib
+
+
+if sys.version_info.major == 3:
+  basestring = (str,)  # pylint: disable=redefined-builtin
+
 
 __version__ = '2.0'
 
@@ -157,14 +154,15 @@ def GetNoGitPagerEnv():
 
 def RunCommand(args, error_ok=False, error_message=None, shell=False, **kwargs):
   try:
-    return subprocess2.check_output(args, shell=shell, **kwargs)
+    stdout = subprocess2.check_output(args, shell=shell, **kwargs)
+    return stdout.decode('utf-8', 'replace')
   except subprocess2.CalledProcessError as e:
     logging.debug('Failed running %s', args)
     if not error_ok:
       DieWithError(
           'Command "%s" failed.\n%s' % (
             ' '.join(args), error_message or e.stdout or ''))
-    return e.stdout
+    return e.stdout.decode('utf-8', 'replace')
 
 
 def RunGit(args, **kwargs):
@@ -183,10 +181,10 @@ def RunGitWithCode(args, suppress_stderr=False):
                                              env=GetNoGitPagerEnv(),
                                              stdout=subprocess2.PIPE,
                                              stderr=stderr)
-    return code, out
+    return code, out.decode('utf-8', 'replace')
   except subprocess2.CalledProcessError as e:
     logging.debug('Failed running %s', ['git'] + args)
-    return e.returncode, e.stdout
+    return e.returncode, e.stdout.decode('utf-8', 'replace')
 
 
 def RunGitSilent(args):
@@ -1017,7 +1015,7 @@ def ParseIssueNumberArgument(arg):
 
   url = gclient_utils.UpgradeToHttps(arg)
   try:
-    parsed_url = urlparse.urlparse(url)
+    parsed_url = urllib.parse.urlparse(url)
   except ValueError:
     return fail_result
 
@@ -1322,7 +1320,7 @@ class Changelist(object):
     url = RunGit(['config', 'remote.%s.url' % remote], error_ok=True).strip()
 
     # Check if the remote url can be parsed as an URL.
-    host = urlparse.urlparse(url).netloc
+    host = urllib.parse.urlparse(url).netloc
     if host:
       self._cached_remote_url = (True, url)
       return url
@@ -1342,7 +1340,7 @@ class Changelist(object):
                  error_ok=True,
                  cwd=url).strip()
 
-    host = urlparse.urlparse(url).netloc
+    host = urllib.parse.urlparse(url).netloc
     if not host:
       logging.error(
           'Remote "%(remote)s" for branch "%(branch)s" points to '
@@ -1655,7 +1653,7 @@ class Changelist(object):
     if self._gerrit_host and '.' not in self._gerrit_host:
       # Abbreviated domain like "chromium" instead of chromium.googlesource.com.
       # This happens for internal stuff http://crbug.com/614312.
-      parsed = urlparse.urlparse(self.GetRemoteUrl())
+      parsed = urllib.parse.urlparse(self.GetRemoteUrl())
       if parsed.scheme == 'sso':
         print('WARNING: using non-https URLs for remote is likely broken\n'
               '  Your current remote is: %s' % self.GetRemoteUrl())
@@ -1668,7 +1666,7 @@ class Changelist(object):
     remote_url = self.GetRemoteUrl()
     if not remote_url:
       return None
-    return urlparse.urlparse(remote_url).netloc
+    return urllib.parse.urlparse(remote_url).netloc
 
   def GetCodereviewServer(self):
     if not self._gerrit_server:
@@ -1678,7 +1676,7 @@ class Changelist(object):
         self._gerrit_server = self._GitGetBranchConfigValue(
             self.CodereviewServerConfigKey())
         if self._gerrit_server:
-          self._gerrit_host = urlparse.urlparse(self._gerrit_server).netloc
+          self._gerrit_host = urllib.parse.urlparse(self._gerrit_server).netloc
       if not self._gerrit_server:
         # We assume repo to be hosted on Gerrit, and hence Gerrit server
         # has "-review" suffix for lowest level subdomain.
@@ -1694,7 +1692,7 @@ class Changelist(object):
     if remote_url is None:
       logging.warn('can\'t detect Gerrit project.')
       return None
-    project = urlparse.urlparse(remote_url).path.strip('/')
+    project = urllib.parse.urlparse(remote_url).path.strip('/')
     if project.endswith('.git'):
       project = project[:-len('.git')]
     # *.googlesource.com hosts ensure that Git/Gerrit projects don't start with
@@ -1743,7 +1741,7 @@ class Changelist(object):
     if not isinstance(cookie_auth, gerrit_util.CookiesAuthenticator):
       return
 
-    if urlparse.urlparse(self.GetRemoteUrl()).scheme != 'https':
+    if urllib.parse.urlparse(self.GetRemoteUrl()).scheme != 'https':
       print('WARNING: Ignoring branch %s with non-https remote %s' %
             (self.branch, self.GetRemoteUrl()))
       return
@@ -1853,7 +1851,7 @@ class Changelist(object):
     try:
       data = self._GetChangeDetail([
           'DETAILED_LABELS', 'CURRENT_REVISION', 'SUBMITTABLE'])
-    except (httplib.HTTPException, GerritChangeNotExists):
+    except GerritChangeNotExists:
       return 'error'
 
     if data['status'] in ('ABANDONED', 'MERGED'):
@@ -1875,7 +1873,7 @@ class Changelist(object):
       return 'unsent'
 
     owner = data['owner'].get('_account_id')
-    messages = sorted(data.get('messages', []), key=lambda m: m.get('updated'))
+    messages = sorted(data.get('messages', []), key=lambda m: m.get('date'))
     last_message_author = messages.pop().get('author', {})
     while last_message_author:
       if last_message_author.get('email') == COMMIT_BOT_EMAIL:
@@ -1902,8 +1900,7 @@ class Changelist(object):
     data = self._GetChangeDetail(['CURRENT_REVISION', 'CURRENT_COMMIT'],
                                  no_cache=force)
     current_rev = data['current_revision']
-    return data['revisions'][current_rev]['commit']['message'].encode(
-        'utf-8', 'ignore')
+    return data['revisions'][current_rev]['commit']['message']
 
   def UpdateDescriptionRemote(self, description, force=False):
     if gerrit_util.HasPendingChangeEdit(
@@ -2324,6 +2321,7 @@ class Changelist(object):
           # Flush after every line: useful for seeing progress when running as
           # recipe.
           filter_fn=lambda _: sys.stdout.flush())
+      push_stdout = push_stdout.decode('utf-8', 'replace')
     except subprocess2.CalledProcessError as e:
       push_returncode = e.returncode
       DieWithError('Failed to create a change. Please examine output above '
@@ -2478,7 +2476,7 @@ class Changelist(object):
                                    options.force, change_desc)
       tree = RunGit(['rev-parse', 'HEAD:']).strip()
       with tempfile.NamedTemporaryFile(delete=False) as desc_tempfile:
-        desc_tempfile.write(change_desc.description)
+        desc_tempfile.write(change_desc.description.encode('utf-8', 'replace'))
         desc_tempfile.close()
         ref_to_push = RunGit(['commit-tree', tree, '-p', parent,
                               '-F', desc_tempfile.name]).strip()
@@ -2528,7 +2526,7 @@ class Changelist(object):
     # Add cc's from the --cc flag.
     if options.cc:
       cc.extend(options.cc)
-    cc = filter(None, [email.strip() for email in cc])
+    cc = [email.strip() for email in cc if email.strip()]
     if change_desc.get_cced():
       cc.extend(change_desc.get_cced())
     if self._GetGerritHost() == 'chromium-review.googlesource.com':
@@ -2729,7 +2727,7 @@ class Changelist(object):
 
   def GetGerritChange(self, patchset=None):
     """Returns a buildbucket.v2.GerritChange message for the current issue."""
-    host = urlparse.urlparse(self.GetCodereviewServer()).hostname
+    host = urllib.parse.urlparse(self.GetCodereviewServer()).hostname
     issue = self.GetIssue()
     patchset = int(patchset or self.GetPatchset())
     data = self._GetChangeDetail(['ALL_REVISIONS'])
@@ -2955,7 +2953,7 @@ class ChangeDescription(object):
       self.append_footer('Bug: %s' % prefix)
 
     content = gclient_utils.RunEditor(self.description, True,
-                                        git_editor=settings.GetGitEditor())
+                                      git_editor=settings.GetGitEditor())
     if not content:
       DieWithError('Running editor failed')
     lines = content.splitlines()
@@ -3193,7 +3191,7 @@ def urlretrieve(source, destination):
   This is necessary because urllib is broken for SSL connections via a proxy.
   """
   with open(destination, 'w') as f:
-    f.write(urllib_request.urlopen(source).read())
+    f.write(urllib.request.urlopen(source).read())
 
 
 def hasSheBang(fname):
@@ -3329,7 +3327,7 @@ class _GitCookiesChecker(object):
     if not hosts:
       print('No Git/Gerrit credentials found')
       return
-    lengths = [max(map(len, (row[i] for row in hosts))) for i in xrange(3)]
+    lengths = [max(map(len, (row[i] for row in hosts))) for i in range(3)]
     header = [('Host', 'User', 'Which file'),
               ['=' * l for l in lengths]]
     for row in (header + hosts):
@@ -3896,7 +3894,7 @@ def CMDstatus(parser, args):
   for cl in sorted(changes, key=lambda c: c.GetBranch()):
     branch = cl.GetBranch()
     while branch not in branch_statuses:
-      c, status = output.next()
+      c, status = next(output)
       branch_statuses[c.GetBranch()] = status
     status = branch_statuses.pop(branch)
     url = cl.GetIssueURL()
@@ -4081,10 +4079,10 @@ def CMDcomments(parser, args):
 
   if options.json_file:
     def pre_serialize(c):
-      dct = c.__dict__.copy()
+      dct = c._asdict().copy()
       dct['date'] = dct['date'].strftime('%Y-%m-%d %H:%M:%S.%f')
       return dct
-    write_json(options.json_file, map(pre_serialize, summary))
+    write_json(options.json_file, [pre_serialize(x) for x in summary])
   return 0
 
 
@@ -4666,7 +4664,7 @@ def GetTreeStatus(url=None):
   'unknown' or 'unset'."""
   url = url or settings.GetTreeStatusUrl(error_ok=True)
   if url:
-    status = urllib_request.urlopen(url).read().lower()
+    status = urllib.request.urlopen(url).read().lower()
     if status.find('closed') != -1 or status == '0':
       return 'closed'
     elif status.find('open') != -1 or status == '1':
@@ -4680,7 +4678,7 @@ def GetTreeStatusReason():
   with the reason for the tree to be opened or closed."""
   url = settings.GetTreeStatusUrl()
   json_url = urlparse.urljoin(url, '/current?format=json')
-  connection = urllib_request.urlopen(json_url)
+  connection = urllib.request.urlopen(json_url)
   status = json.loads(connection.read())
   connection.close()
   return status['message']
@@ -5446,7 +5444,7 @@ class OptionParser(optparse.OptionParser):
     # Store the options passed by the user in an _actual_options attribute.
     # We store only the keys, and not the values, since the values can contain
     # arbitrary information, which might be PII.
-    metrics.collector.add('arguments', actual_options.__dict__.keys())
+    metrics.collector.add('arguments', list(actual_options.__dict__.keys()))
 
     levels = [logging.WARNING, logging.INFO, logging.DEBUG]
     logging.basicConfig(
@@ -5469,7 +5467,7 @@ def main(argv):
     return dispatcher.execute(OptionParser(), argv)
   except auth.LoginRequiredError as e:
     DieWithError(str(e))
-  except urllib_error.HTTPError as e:
+  except urllib.error.HTTPError as e:
     if e.code != 500:
       raise
     DieWithError(

tests/git_cl_test.py

@@ -10,11 +10,9 @@ import json
 import logging
 import os
 import shutil
-import StringIO
 import sys
 import tempfile
 import unittest
-import urlparse
 
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
@@ -31,6 +29,11 @@ import git_common
 import git_footers
 import subprocess2
 
+if sys.version_info.major == 2:
+  from StringIO import StringIO
+else:
+  from io import StringIO
+
 
 def callError(code=1, cmd='', cwd='', stdout='', stderr=''):
   return subprocess2.CalledProcessError(code, cmd, cwd, stdout, stderr)
@@ -571,13 +574,13 @@ class GitCookiesCheckerTest(TestCase):
 
   def test_report_no_problems(self):
     self.test_analysis_nothing()
-    self.mock(sys, 'stdout', StringIO.StringIO())
+    self.mock(sys, 'stdout', StringIO())
     self.assertFalse(self.c.find_and_report_problems())
     self.assertEqual(sys.stdout.getvalue(), '')
 
   def test_report(self):
     self.test_analysis()
-    self.mock(sys, 'stdout', StringIO.StringIO())
+    self.mock(sys, 'stdout', StringIO())
     self.mock(git_cl.gerrit_util.CookiesAuthenticator, 'get_gitcookies_path',
               classmethod(lambda _: '~/.gitcookies'))
     self.assertTrue(self.c.find_and_report_problems())
@@ -713,7 +716,7 @@ class TestGitCl(TestCase):
     self.assertTrue(git_cl.ask_for_explicit_yes('prompt'))
 
   def test_LoadCodereviewSettingsFromFile_gerrit(self):
-    codereview_file = StringIO.StringIO('GERRIT_HOST: true')
+    codereview_file = StringIO('GERRIT_HOST: true')
     self.calls = [
       ((['git', 'config', '--unset-all', 'rietveld.cc'],), CERR1),
       ((['git', 'config', '--unset-all', 'rietveld.tree-status-url'],), CERR1),
@@ -1240,7 +1243,7 @@ class TestGitCl(TestCase):
 
     reviewers = reviewers or []
     cc = cc or []
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self.mock(git_cl.gerrit_util, 'CookiesAuthenticator',
               CookiesAuthenticatorMockFactory(
                 same_auth=('git-owner.example.com', '', 'pass')))
@@ -1354,7 +1357,7 @@ class TestGitCl(TestCase):
         change_id='I123456789')
 
   def test_gerrit_patchset_title_special_chars(self):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self._run_gerrit_upload_test(
         ['-f', '-t', 'We\'ll escape ^_ ^ special chars...@{u}'],
         'desc\n\nBUG=\n\nChange-Id: I123456789',
@@ -1520,7 +1523,7 @@ class TestGitCl(TestCase):
         git_cl.sys.stdout.getvalue())
 
   def test_upload_branch_deps(self):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     def mock_run_git(*args, **_kwargs):
       if args[0] == ['for-each-ref',
                        '--format=%(refname:short) %(upstream:short)',
@@ -1778,7 +1781,7 @@ class TestGitCl(TestCase):
                     detect_gerrit_server=False,
                     actual_codereview=None,
                     codereview_in_url=False):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self.mock(git_cl, 'IsGitVersionAtLeast', lambda *args: True)
 
     if new_branch:
@@ -1972,13 +1975,13 @@ class TestGitCl(TestCase):
 
   def test_checkout_not_found(self):
     """Tests git cl checkout <issue>."""
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self.calls = self._checkout_calls()
     self.assertEqual(1, git_cl.main(['checkout', '99999']))
 
   def test_checkout_no_branch_issues(self):
     """Tests git cl checkout <issue>."""
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self.calls = [
         ((['git', 'config', '--local', '--get-regexp',
            'branch\\..*\\.gerritissue'], ), CERR1),
@@ -2011,7 +2014,7 @@ class TestGitCl(TestCase):
     self.assertIsNone(cl.EnsureAuthenticated(force=False))
 
   def test_gerrit_ensure_authenticated_conflict(self):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     cl = self._test_gerrit_ensure_authenticated_common(auth={
       'chromium.googlesource.com':
           ('git-one.example.com', None, 'secret1'),
@@ -2097,7 +2100,7 @@ class TestGitCl(TestCase):
     self.assertEqual(0, git_cl.main(['set-commit']))
 
   def test_description_display(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stdout', out)
 
     self.mock(git_cl, 'Changelist', ChangelistMock)
@@ -2107,7 +2110,7 @@ class TestGitCl(TestCase):
     self.assertEqual('foo\n', out.getvalue())
 
   def test_StatusFieldOverrideIssueMissingArgs(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stderr', out)
 
     try:
@@ -2116,7 +2119,7 @@ class TestGitCl(TestCase):
       self.assertEqual(ex.code, 2)
       self.assertRegexpMatches(out.getvalue(), r'--field must be specified')
 
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stderr', out)
 
     try:
@@ -2126,7 +2129,7 @@ class TestGitCl(TestCase):
       self.assertRegexpMatches(out.getvalue(), r'--field must be specified')
 
   def test_StatusFieldOverrideIssue(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stdout', out)
 
     def assertIssue(cl_self, *_args):
@@ -2151,7 +2154,7 @@ class TestGitCl(TestCase):
       git_cl.main(['set-close', '--issue', '1', '--gerrit']), 0)
 
   def test_description(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stdout', out)
     self.calls = [
         ((['git', 'symbolic-ref', 'HEAD'],), 'feature'),
@@ -2175,11 +2178,11 @@ class TestGitCl(TestCase):
     self.assertEqual('foobar\n', out.getvalue())
 
   def test_description_set_raw(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stdout', out)
 
     self.mock(git_cl, 'Changelist', ChangelistMock)
-    self.mock(git_cl.sys, 'stdin', StringIO.StringIO('hihi'))
+    self.mock(git_cl.sys, 'stdin', StringIO('hihi'))
 
     self.assertEqual(0, git_cl.main(['description', '-n', 'hihi']))
     self.assertEqual('hihi', ChangelistMock.desc)
@@ -2202,7 +2205,7 @@ class TestGitCl(TestCase):
     def UpdateDescriptionRemote(_, desc, force=False):
       self.assertEqual(desc, 'Some.\n\nChange-Id: xxx\nBug: 123')
 
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self.mock(git_cl.Changelist, 'GetDescription',
               lambda *args: current_desc)
     self.mock(git_cl.Changelist, 'UpdateDescriptionRemote',
@@ -2232,7 +2235,7 @@ class TestGitCl(TestCase):
           desc)
       return desc
 
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self.mock(git_cl.Changelist, 'GetDescription',
               lambda *args: current_desc)
     self.mock(git_cl.gclient_utils, 'RunEditor', RunEditor)
@@ -2247,17 +2250,17 @@ class TestGitCl(TestCase):
     self.assertEqual(0, git_cl.main(['description', '--gerrit']))
 
   def test_description_set_stdin(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stdout', out)
 
     self.mock(git_cl, 'Changelist', ChangelistMock)
-    self.mock(git_cl.sys, 'stdin', StringIO.StringIO('hi \r\n\t there\n\nman'))
+    self.mock(git_cl.sys, 'stdin', StringIO('hi \r\n\t there\n\nman'))
 
     self.assertEqual(0, git_cl.main(['description', '-n', '-']))
     self.assertEqual('hi\n\t there\n\nman', ChangelistMock.desc)
 
   def test_archive(self):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
 
     self.calls = [
       ((['git', 'for-each-ref', '--format=%(refname)', 'refs/heads'],),
@@ -2276,7 +2279,7 @@ class TestGitCl(TestCase):
     self.assertEqual(0, git_cl.main(['archive', '-f']))
 
   def test_archive_current_branch_fails(self):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self.calls = [
       ((['git', 'for-each-ref', '--format=%(refname)', 'refs/heads'],),
          'refs/heads/master'),
@@ -2290,7 +2293,7 @@ class TestGitCl(TestCase):
     self.assertEqual(1, git_cl.main(['archive', '-f']))
 
   def test_archive_dry_run(self):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
 
     self.calls = [
       ((['git', 'for-each-ref', '--format=%(refname)', 'refs/heads'],),
@@ -2307,7 +2310,7 @@ class TestGitCl(TestCase):
     self.assertEqual(0, git_cl.main(['archive', '-f', '--dry-run']))
 
   def test_archive_no_tags(self):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
 
     self.calls = [
       ((['git', 'for-each-ref', '--format=%(refname)', 'refs/heads'],),
@@ -2325,7 +2328,7 @@ class TestGitCl(TestCase):
     self.assertEqual(0, git_cl.main(['archive', '-f', '--notags']))
 
   def test_cmd_issue_erase_existing(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stdout', out)
     self.calls = [
         ((['git', 'symbolic-ref', 'HEAD'],), 'feature'),
@@ -2342,7 +2345,7 @@ class TestGitCl(TestCase):
     self.assertEqual(0, git_cl.main(['issue', '0']))
 
   def test_cmd_issue_erase_existing_with_change_id(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stdout', out)
     self.mock(git_cl.Changelist, 'GetDescription',
               lambda _: 'This is a description\n\nChange-Id: Ideadbeef')
@@ -2363,7 +2366,7 @@ class TestGitCl(TestCase):
     self.assertEqual(0, git_cl.main(['issue', '0']))
 
   def test_cmd_issue_json(self):
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(git_cl.sys, 'stdout', out)
     self.calls = [
         ((['git', 'symbolic-ref', 'HEAD'],), 'feature'),
@@ -2378,7 +2381,7 @@ class TestGitCl(TestCase):
     self.assertEqual(0, git_cl.main(['issue', '--json', 'output.json']))
 
   def _common_GerritCommitMsgHookCheck(self):
-    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+    self.mock(git_cl.sys, 'stdout', StringIO())
     self.mock(git_cl.os.path, 'abspath',
               lambda path: self._mocked_call(['abspath', path]))
     self.mock(git_cl.os.path, 'exists',
@@ -2441,7 +2444,7 @@ class TestGitCl(TestCase):
                      'url': 'https://git.googlesource.com/test/+/deadbeef'}],
     }
     cl.SubmitIssue = lambda wait_for_merge: None
-    out = StringIO.StringIO()
+    out = StringIO()
     self.mock(sys, 'stdout', out)
     self.assertEqual(0, cl.CMDLand(force=True,
                                    bypass_hooks=True,
@@ -2537,7 +2540,7 @@ class TestGitCl(TestCase):
         }
     self.mock(git_cl.gerrit_util, 'CookiesAuthenticator',
               CookiesAuthenticatorMock)
-    self.mock(sys, 'stdout', StringIO.StringIO())
+    self.mock(sys, 'stdout', StringIO())
     git_cl._GitCookiesChecker().print_current_creds(include_netrc=True)
     self.assertEqual(list(sys.stdout.getvalue().splitlines()), [
         '                        Host\t User\t Which file',
@@ -2546,7 +2549,8 @@ class TestGitCl(TestCase):
         '       host.googlesource.com\t user\t.gitcookies',
         '      host2.googlesource.com\tuser3\t     .netrc',
     ])
-    sys.stdout.buf = ''
+    sys.stdout.seek(0)
+    sys.stdout.truncate(0)
     git_cl._GitCookiesChecker().print_current_creds(include_netrc=False)
     self.assertEqual(list(sys.stdout.getvalue().splitlines()), [
         '                        Host\tUser\t Which file',
@@ -2566,7 +2570,7 @@ class TestGitCl(TestCase):
       # git cl also checks for existence other files not relevant to this test.
       return None
     self.mock(os.path, 'exists', exists_mock)
-    self.mock(sys, 'stdout', StringIO.StringIO())
+    self.mock(sys, 'stdout', StringIO())
 
   def test_creds_check_gitcookies_not_configured(self):
     self._common_creds_check_mocks()
@@ -2631,7 +2635,7 @@ class TestGitCl(TestCase):
                                      '-a', 'msg']))
 
   def test_git_cl_comments_fetch_gerrit(self):
-    self.mock(sys, 'stdout', StringIO.StringIO())
+    self.mock(sys, 'stdout', StringIO())
     self.calls = [
       ((['git', 'config', 'branch.foo.gerritserver'],), ''),
       ((['git', 'config', 'branch.foo.merge'],), ''),
@@ -2782,7 +2786,7 @@ class TestGitCl(TestCase):
     # git cl comments also fetches robot comments (which are considered a type
     # of autogenerated comment), and unlike other types of comments, only robot
     # comments from the latest patchset are shown.
-    self.mock(sys, 'stdout', StringIO.StringIO())
+    self.mock(sys, 'stdout', StringIO())
     self.calls = [
       ((['git', 'config', 'branch.foo.gerritserver'],), ''),
       ((['git', 'config', 'branch.foo.merge'],), ''),
@@ -3037,7 +3041,7 @@ class CMDTestCaseBase(unittest.TestCase):
 
   def setUp(self):
     super(CMDTestCaseBase, self).setUp()
-    mock.patch('git_cl.sys.stdout', StringIO.StringIO()).start()
+    mock.patch('git_cl.sys.stdout', StringIO()).start()
     mock.patch('git_cl.uuid.uuid4', return_value='uuid4').start()
     mock.patch('git_cl.Changelist.GetIssue', return_value=123456).start()
     mock.patch('git_cl.Changelist.GetCodereviewServer',