Uses commit hash instead of version tags in pre-commit

Change-Id: Ibc68475503aba33b04ae01ac9de580bb80e372b4
Signed-off-by: Moisés Guimarães de Medeiros <moguimar@redhat.com>

.pre-commit-config.yaml

@@ -1,10 +1,16 @@
 ---
+# 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: ebc15addedad713c86ef18ae9632c88e187dd0af  # v3.1.0
     hooks:
       - id: trailing-whitespace
       # Replaces or checks mixed line ending
@@ -23,7 +29,7 @@ repos:
       - id: check-yaml
         files: .*\.(yaml|yml)$
   - repo: https://gitlab.com/pycqa/flake8
-    rev: 3.8.3
+    rev: 181bb46098dddf7e2d45319ea654b4b4d58c2840 # 3.8.3
     hooks:
       - id: flake8
         additional_dependencies: