Move flake8 as a pre-commit local target.

The goal here is to avoid conflicts between flake8 and hacking version each
2 days.

Inspired from nova's approach[1].

The flake8 version to install will be determined by hacking and
requirements[2] will stay aligned instead of relying on different versions.

[1] https://opendev.org/openstack/nova/src/branch/master/.pre-commit-config.yaml#L26-L35
[2] https://opendev.org/openstack/hacking/src/branch/master/requirements.txt#L1

Change-Id: I9ffd46865477b3fa7d43258d67dd0ec224ee6467

.pre-commit-config.yaml

@@ -1,10 +1,15 @@
----
+# 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:
-  # force all unspecified python hooks to run python3
   python: python3
+
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v3.1.0
+    rev: 9136088a246768144165fcc3ecc3d31bb686920a # v3.3.0
     hooks:
       - id: trailing-whitespace
       # Replaces or checks mixed line ending
@@ -22,14 +27,13 @@ repos:
       - id: debug-statements
       - id: check-yaml
         files: .*\.(yaml|yml)$
-  - repo: https://github.com/Lucas-C/pre-commit-hooks
-    rev: v1.1.7
-    hooks:
-      - id: remove-tabs
-        exclude: '.*\.(svg)$'
-  - repo: https://gitlab.com/pycqa/flake8
-    rev: 3.8.3
+  - repo: local
     hooks:
       - id: flake8
+        name: flake8
         additional_dependencies:
           - hacking>=3.0.1,<3.1.0
+        language: python
+        entry: flake8
+        files: '^.*\.py$'
+        exclude: '^(doc|releasenotes|tools)/.*$'