Adding pre-commit

Introduced changes:
- pre-commit config and rules
- Add pre-commit to pep8 gate, Flake8 is covered in the pre-commit hooks.
- Applying fixes for pre-commit compliance in all code.

Also commit hash will be used instead of version tags in pre-commit to
prevend arbitrary code from running in developer's machines.

pre-commit will be used to:
- trailing whitespace;
- Replaces or checks mixed line ending (mixed-line-ending);
- Forbid files which have a UTF-8 byte-order marker (check-byte-order-marker);
- Checks that non-binary executables have a proper
  shebang (check-executables-have-shebangs);
- Check for files that contain merge conflict strings (check-merge-conflict);
- Check for debugger imports and py37+ breakpoint()
  calls in python source (debug-statements);
- Attempts to load all yaml files to verify syntax (check-yaml);
- Run flake8 checks (flake8) (local)

For further details about tests please refer to:
https://github.com/pre-commit/pre-commit-hooks

Change-Id: I60e74ffcc7a4cc5...

.pre-commit-config.yaml

+# We from the Oslo project decided to pin repos based on the
+# commit hash instead of the version tag to prevend arbitrary
+# code from running in developer's machines.  To update to a
+# newer version, run `pre-commit autoupdate` and then replace
+# the newer versions with their commit hash.
+
+default_language_version:
+  python: python3
+
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: ebc15addedad713c86ef18ae9632c88e187dd0af  # v3.1.0
+    hooks:
+      - id: trailing-whitespace
+      # Replaces or checks mixed line ending
+      - id: mixed-line-ending
+        args: ['--fix', 'lf']
+        exclude: '.*\.(svg)$'
+      # Forbid files which have a UTF-8 byte-order marker
+      - id: check-byte-order-marker
+      # Checks that non-binary executables have a proper shebang
+      - id: check-executables-have-shebangs
+      # Check for files that contain merge conflict strings.
+      - id: check-merge-conflict
+      # Check for debugger imports and py37+ breakpoint()
+      # calls in python source
+      - id: debug-statements
+      - id: check-yaml
+        files: .*\.(yaml|yml)$
+  - repo: https://gitlab.com/pycqa/flake8
+    rev: 181bb46098dddf7e2d45319ea654b4b4d58c2840 # 3.8.3
+    hooks:
+      - id: flake8
+        additional_dependencies:
+          - hacking>=3.0.1,<3.1.0

doc/source/conf.py

 # -*- coding: utf-8 -*-
+# Copyright (C) 2020 Red Hat, Inc.
+#
 # 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
@@ -85,6 +87,3 @@ latex_documents = [
      u'%s Documentation' % project,
      u'OpenStack Foundation', 'manual'),
 ]
-
-# Example configuration for intersphinx: refer to the Python standard library.
-#intersphinx_mapping = {'http://docs.python.org/': None}

test-requirements.txt

@@ -12,3 +12,5 @@ fixtures>=3.0.0 # Apache-2.0/BSD
 
 # Bandit security code scanner
 bandit>=1.6.0,<1.7.0 # Apache-2.0
+
+pre-commit>=2.6.0 # MIT

tox.ini

@@ -12,7 +12,7 @@ commands = stestr run --slowest {posargs}
 
 [testenv:pep8]
 commands =
-  flake8
+  pre-commit run -a
   # Run security linter
   bandit -r oslo_versionedobjects tests -n5 --skip B303