Run pyupgrade to clean up Python 2 syntaxes

Update all .py source files by
 $ pyupgrade --py3-only $(git ls-files | grep ".py$")
to modernize the code according to Python 3 syntaxes.

Also introduce pre-commit and its pyupgrade hook to avoid merging
additional Python 2 syntaxes.

Change-Id: I12d2ccc679e0fcb3e3f467ee59da0aabb61a04a2

.pre-commit-config.yaml

@@ -23,3 +23,8 @@ repos:
     hooks:
       - id: hacking
         additional_dependencies: []
+  - repo: https://github.com/asottile/pyupgrade
+    rev: v3.18.0
+    hooks:
+      - id: pyupgrade
+        args: [--py3-only]

doc/source/conf.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (C) 2020 Red Hat, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License"); you may

oslo_upgradecheck/tests/test_common_checks.py

@@ -28,7 +28,7 @@ from oslo_upgradecheck import upgradecheck
 class TestUpgradeCheckPolicyJSON(base.BaseTestCase):
 
     def setUp(self):
-        super(TestUpgradeCheckPolicyJSON, self).setUp()
+        super().setUp()
         conf_fixture = self.useFixture(config.Config())
         conf_fixture.load_raw_values()
         self.conf = conf_fixture.conf

oslo_upgradecheck/tests/test_upgradecheck.py

@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 # Licensed under the Apache License, Version 2.0 (the "License"); you may
 # not use this file except in compliance with the License. You may obtain
 # a copy of the License at

oslo_upgradecheck/upgradecheck.py

@@ -50,7 +50,7 @@ UPGRADE_CHECK_MSG_MAP = {
 }
 
 
-class Result(object):
+class Result:
     """Class used for 'nova-status upgrade check' results.
 
     The 'code' attribute is a Code enum.
@@ -60,12 +60,12 @@ class Result(object):
     """
 
     def __init__(self, code, details=None):
-        super(Result, self).__init__()
+        super().__init__()
         self.code = code
         self.details = details
 
 
-class UpgradeCommands(object):
+class UpgradeCommands:
     """Base class for upgrade checks
 
     This class should be inherited by a class in each project that provides

releasenotes/source/conf.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (C) 2020 Red Hat, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License"); you may