diff --git a/BUILD.gn b/BUILD.gn
index dfce359101..2c07ca8060 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2,8 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//build/config/python.gni")
-
 import("./config/gni/all_devtools_files.gni")
 import("./config/gni/devtools_grd_files.gni")
 import("./config/gni/devtools_image_files.gni")
@@ -247,8 +245,7 @@ if (!is_debug) {
   build_release_devtools_args += [ "--rollup" ]
 }
 
-# TODO(crbug.com/1112471): Get this to work cleanly under Python3.
-python2_action("build_release_devtools") {
+action("build_release_devtools") {
   script = "scripts/build/build_release_applications.py"
 
   helper_scripts = [
diff --git a/inspector_overlay/BUILD.gn b/inspector_overlay/BUILD.gn
index e7364dce9d..109aa82091 100644
--- a/inspector_overlay/BUILD.gn
+++ b/inspector_overlay/BUILD.gn
@@ -2,13 +2,11 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//build/config/python.gni")
 import("../third_party/typescript/typescript.gni")
 
 resources_out_dir = "$root_out_dir/resources/inspector_overlay"
 
-# TODO(crbug.com/1112471): Get this to work under Python 3.
-python2_action("build_inspector_overlay") {
+action("build_inspector_overlay") {
   script = "../scripts/build/build_inspector_overlay.py"
 
   inputs = [
diff --git a/scripts/build/build_inspector_overlay.py b/scripts/build/build_inspector_overlay.py
index 64f1c4906c..d1ac109340 100644
--- a/scripts/build/build_inspector_overlay.py
+++ b/scripts/build/build_inspector_overlay.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env vpython
-# -*- coding: UTF-8 -*-
+# -*- coding: utf-8 -*-
 #
 # Copyright 2020 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -44,7 +44,9 @@ def rollup(input_path, output_path, filename, max_size, rollup_plugin):
         ['--format', 'iife', '-n', 'InspectorOverlay'] + ['--input', target] +
         ['--plugin', rollup_plugin, '--plugin', 'terser'],
         stdout=subprocess.PIPE,
-        stderr=subprocess.PIPE)
+        stderr=subprocess.PIPE,
+        universal_newlines=True,
+        encoding='utf-8')
     out, error = rollup_process.communicate()
     if not out:
         raise Exception("rollup failed: " + error)
diff --git a/scripts/build/build_release_applications.py b/scripts/build/build_release_applications.py
index 531e56716d..88079a84e6 100644
--- a/scripts/build/build_release_applications.py
+++ b/scripts/build/build_release_applications.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env vpython
-# -*- coding: UTF-8 -*-
+# -*- coding: utf-8 -*-
 #
 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -10,7 +10,7 @@ Builds applications in release mode:
 and the application loader into a single script.
 """
 
-from cStringIO import StringIO
+from io import StringIO
 from os import path
 from os.path import join
 import copy
@@ -152,8 +152,7 @@ class ReleaseBuilder(object):
             resource_content = read_file(path.join(self.application_dir, resource_name))
             if not (resource_name.endswith('.html')
                     or resource_name.endswith('md')):
-                resource_content += resource_source_url(resource_name).encode(
-                    'utf-8')
+                resource_content += resource_source_url(resource_name)
             resource_content = resource_content.replace('\\', '\\\\')
             resource_content = resource_content.replace('\n', '\\n')
             resource_content = resource_content.replace('"', '\\"')
@@ -179,7 +178,9 @@ class ReleaseBuilder(object):
     def _concatenate_application_script(self, output):
         output.write('Root.allDescriptors.push(...%s);' % self._release_module_descriptors())
         if self.descriptors.extends:
-            output.write('Root.applicationDescriptor.modules.push(...%s);' % json.dumps(self.descriptors.application.values()))
+            output.write(
+                'Root.applicationDescriptor.modules.push(...%s);' %
+                json.dumps(list(self.descriptors.application.values())))
         else:
             output.write('Root.applicationDescriptor = %s;' % self.descriptors.application_json())
 
diff --git a/scripts/build/modular_build.py b/scripts/build/modular_build.py
index 9018db285c..0c3461db6e 100644
--- a/scripts/build/modular_build.py
+++ b/scripts/build/modular_build.py
@@ -20,7 +20,7 @@ except ImportError:
 
 
 def read_file(filename):
-    with open(path.normpath(filename), 'rt') as input:
+    with open(path.normpath(filename), 'rt', encoding='utf-8') as input:
         return input.read()
 
 
@@ -30,7 +30,7 @@ def write_file(filename, content):
     directory = path.dirname(filename)
     if not path.exists(directory):
         os.makedirs(directory)
-    with open(filename, 'wt') as output:
+    with open(filename, 'wt', encoding='utf-8') as output:
         output.write(content)
 
 
@@ -59,7 +59,7 @@ class Descriptors:
 
     def application_json(self):
         result = dict()
-        result['modules'] = self.application.values()
+        result['modules'] = list(self.application.values())
         return json.dumps(result)
 
     def module_resources(self, name):
@@ -70,7 +70,10 @@ class Descriptors:
             return self._cached_sorted_modules
 
         result = []
-        unvisited_modules = set(self.modules)
+
+        # Use dict instead of set for deterministic iteration order.
+        unvisited_modules = {module: None for module in self.modules}
+
         temp_modules = set()
 
         def visit(parent, name):
@@ -87,7 +90,7 @@ class Descriptors:
                     bad_dep = visit(name, dep_name)
                     if bad_dep:
                         return bad_dep
-            unvisited_modules.remove(name)
+            del unvisited_modules[name]
             temp_modules.remove(name)
             result.append(name)
             return None