diff --git a/cit b/cit
index 410341ff9..db4c605e8 100755
--- a/cit
+++ b/cit
@@ -5,4 +5,4 @@
 
 base_dir=$(dirname "$0")
 
-PYTHONDONTWRITEBYTECODE=1 exec python "$base_dir/cit.py" "$@"
+PYTHONDONTWRITEBYTECODE=1 exec python3 "$base_dir/cit.py" "$@"
diff --git a/cit.bat b/cit.bat
index 82919b936..c1157ecfe 100755
--- a/cit.bat
+++ b/cit.bat
@@ -9,4 +9,4 @@ setlocal
 set PATH=%PATH%;%~dp0
 
 :: Defer control.
-python "%~dp0\cit.py" %*
+python3 "%~dp0\cit.py" %*
diff --git a/cit.py b/cit.py
index 09de655db..3058f44fe 100755
--- a/cit.py
+++ b/cit.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright (c) 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/clang-format b/clang-format
index c3715403e..35a1168de 100755
--- a/clang-format
+++ b/clang-format
@@ -5,4 +5,4 @@
 
 base_dir=$(dirname "$0")
 
-PYTHONDONTWRITEBYTECODE=1 exec python "$base_dir/clang_format.py" "$@"
+PYTHONDONTWRITEBYTECODE=1 exec python3 "$base_dir/clang_format.py" "$@"
diff --git a/clang-format.bat b/clang-format.bat
index c3bb53bc4..4e0c80f34 100644
--- a/clang-format.bat
+++ b/clang-format.bat
@@ -9,4 +9,4 @@ setlocal
 set PATH=%PATH%;%~dp0
 
 :: Defer control.
-python "%~dp0\clang_format.py" %*
+python3 "%~dp0\clang_format.py" %*
diff --git a/clang_format.py b/clang_format.py
index b7b60a8f7..64f4c6ea4 100755
--- a/clang_format.py
+++ b/clang_format.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/clang_format_merge_driver b/clang_format_merge_driver
index 8b7904946..7298c5415 100755
--- a/clang_format_merge_driver
+++ b/clang_format_merge_driver
@@ -5,4 +5,4 @@
 
 base_dir=$(dirname "$0")
 
-PYTHONDONTWRITEBYTECODE=1 exec python "$base_dir/clang_format_merge_driver.py" "$@"
+PYTHONDONTWRITEBYTECODE=1 exec python3 "$base_dir/clang_format_merge_driver.py" "$@"
diff --git a/clang_format_merge_driver.bat b/clang_format_merge_driver.bat
index 8e614b492..a49ca1a5b 100755
--- a/clang_format_merge_driver.bat
+++ b/clang_format_merge_driver.bat
@@ -9,4 +9,4 @@ setlocal
 set PATH=%PATH%;%~dp0
 
 :: Defer control.
-python "%~dp0\clang_format_merge_driver.py" %*
+python3 "%~dp0\clang_format_merge_driver.py" %*
diff --git a/clang_format_merge_driver.py b/clang_format_merge_driver.py
index 86e803372..2e5211c41 100755
--- a/clang_format_merge_driver.py
+++ b/clang_format_merge_driver.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/compile_single_file b/compile_single_file
index e65816cc1..33c23c69e 100755
--- a/compile_single_file
+++ b/compile_single_file
@@ -5,4 +5,4 @@
 
 base_dir=$(dirname "$0")
 
-PYTHONDONTWRITEBYTECODE=1 exec python -u "$base_dir/compile_single_file.py" "$@"
+PYTHONDONTWRITEBYTECODE=1 exec python3 -u "$base_dir/compile_single_file.py" "$@"
diff --git a/compile_single_file.bat b/compile_single_file.bat
index 84ff3484f..598f9f221 100644
--- a/compile_single_file.bat
+++ b/compile_single_file.bat
@@ -8,4 +8,4 @@ setlocal
 :: standalone, but allow other PATH manipulations to take priority.
 set PATH=%PATH%;%~dp0
 
-python -u "%~dp0compile_single_file.py" %*
+python3 -u "%~dp0compile_single_file.py" %*
diff --git a/compile_single_file.py b/compile_single_file.py
index 833e03ef6..bb0a5416d 100644
--- a/compile_single_file.py
+++ b/compile_single_file.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/git-runhooks b/git-runhooks
index 5bb503e51..df275bf2b 100755
--- a/git-runhooks
+++ b/git-runhooks
@@ -15,9 +15,9 @@ gclient_spec="solutions=[{'name':'src','url':None,'deps_file':'.DEPS.git'}]"
 kernel_name=$(uname -s)
 if [ "${kernel_name:0:5}" = "MINGW" ]; then
   dir="${0%\\*}"
-  cmd "/C ${dir}\\python.bat ${dir}\\gclient.py runhooks --spec=$gclient_spec"
+  cmd "/C ${dir}\\python3.bat ${dir}\\gclient.py runhooks --spec=$gclient_spec"
 else
   dir="$(dirname $0)"
-  PYTHONDONTWRITEBYTECODE=1 exec python "$dir/gclient.py" runhooks --spec="$gclient_spec"
+  PYTHONDONTWRITEBYTECODE=1 exec python3 "$dir/gclient.py" runhooks --spec="$gclient_spec"
 fi
 exit $?
diff --git a/testing_support/cipd b/testing_support/cipd
index 21519a129..6d2929c93 100755
--- a/testing_support/cipd
+++ b/testing_support/cipd
@@ -5,4 +5,4 @@
 
 base_dir=$(dirname "$0")
 
-exec python "$base_dir/fake_cipd.py" "$@"
+exec python3 "$base_dir/fake_cipd.py" "$@"
diff --git a/testing_support/cipd.bat b/testing_support/cipd.bat
index a1a941061..f5b6df7dd 100755
--- a/testing_support/cipd.bat
+++ b/testing_support/cipd.bat
@@ -5,4 +5,4 @@ echo off
 setlocal
 
 :: Defer control.
-python "%~dp0fake_cipd.py" %*
+python3 "%~dp0fake_cipd.py" %*
diff --git a/testing_support/fake_cipd.py b/testing_support/fake_cipd.py
index 9bb3cf10b..1dab00663 100644
--- a/testing_support/fake_cipd.py
+++ b/testing_support/fake_cipd.py
@@ -1,9 +1,10 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright (c) 2018 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import argparse
+import io
 import os
 import re
 import shutil
@@ -20,8 +21,10 @@ def parse_cipd(root, contents):
     line = line.strip()
     match = re.match(CIPD_SUBDIR_RE, line)
     if match:
+      print('match')
       current_subdir = os.path.join(root, *match.group(1).split('/'))
     elif line and current_subdir:
+      print('no match')
       tree.setdefault(current_subdir, []).append(line)
   return tree
 
@@ -33,15 +36,15 @@ def main():
   parser.add_argument('-root')
   args, _ = parser.parse_known_args()
 
-  with open(args.ensure_file) as f:
+  with io.open(args.ensure_file, 'r', encoding='utf-8') as f:
     new_content = parse_cipd(args.root, f.readlines())
 
   # Install new packages
   for path, packages in new_content.items():
     if not os.path.exists(path):
       os.makedirs(path)
-    with open(os.path.join(path, '_cipd'), 'wb') as f:
-      f.write('\n'.join(packages).encode('utf-8', 'replace'))
+    with io.open(os.path.join(path, '_cipd'), 'w', encoding='utf-8') as f:
+      f.write('\n'.join(packages))
 
   # Save the ensure file that we got
   shutil.copy(args.ensure_file, os.path.join(args.root, '_cipd'))
diff --git a/testing_support/fake_repos.py b/testing_support/fake_repos.py
index c4a4da580..ba2441c6a 100755
--- a/testing_support/fake_repos.py
+++ b/testing_support/fake_repos.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -11,6 +11,7 @@ from __future__ import print_function
 import atexit
 import datetime
 import errno
+import io
 import logging
 import os
 import pprint
@@ -49,7 +50,8 @@ def read_tree(tree_root):
     for f in [join(root, f) for f in files if not f.startswith('.')]:
       filepath = f[len(tree_root) + 1:].replace(os.sep, '/')
       assert len(filepath), f
-      tree[filepath] = gclient_utils.FileRead(join(root, f))
+      with io.open(join(root, f), encoding='utf-8') as f:
+        tree[filepath] = f.read()
   return tree