chore: new owl bot post processor docker image (#188)

gcr.io/repo-automation-bots/owlbot-python:latest@sha256:4c981a6b6f2b8914a448d7b3a01688365be03e3ed26dfee399a6aa77fb112eaa

.github/.OwlBot.lock.yaml

@@ -1,4 +1,3 @@
 docker:
-  digest: sha256:cfc0e802701262c211703c468874d767f65dabe6a1a71d0e07bfc8a3d5175f32
-  image: gcr.io/repo-automation-bots/owlbot-python:latest  
-
+  image: gcr.io/repo-automation-bots/owlbot-python:latest
+  digest: sha256:4c981a6b6f2b8914a448d7b3a01688365be03e3ed26dfee399a6aa77fb112eaa

.pre-commit-config.yaml

@@ -26,6 +26,6 @@ repos:
     hooks:
     - id: black
 -   repo: https://gitlab.com/pycqa/flake8
-    rev: 3.9.0
+    rev: 3.9.2
     hooks:
     - id: flake8

CONTRIBUTING.rst

@@ -160,21 +160,7 @@ Running System Tests
   auth settings and change some configuration in your project to
   run all the tests.
 
-- System tests will be run against an actual project and
-  so you'll need to provide some environment variables to facilitate
-  authentication to your project:
-
-  - ``GOOGLE_APPLICATION_CREDENTIALS``: The path to a JSON key file;
-    Such a file can be downloaded directly from the developer's console by clicking
-    "Generate new JSON key". See private key
-    `docs <https://cloud.google.com/storage/docs/authentication#generating-a-private-key>`__
-    for more details.
-
-- Once you have downloaded your json keys, set the environment variable 
-  ``GOOGLE_APPLICATION_CREDENTIALS`` to the absolute path of the json file::
-
-   $ export GOOGLE_APPLICATION_CREDENTIALS="/Users/<your_username>/path/to/app_credentials.json"
-
+- System tests will be run against an actual project. You should use local credentials from gcloud when possible. See `Best practices for application authentication <https://cloud.google.com/docs/authentication/best-practices-applications#local_development_and_testing_with_the>`__. Some tests require a service account. For those tests see `Authenticating as a service account <https://cloud.google.com/docs/authentication/production>`__.
 
 *************
 Test Coverage