chore(python): update release.sh to use keystore (#72)

Source-Link: googleapis/synthtool@69fda12
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:ae600f36b6bc972b368367b6f83a1d91ec2c82a4a116b383d67d547c56fe6de3

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <partheniou@google.com>

packages/google-cloud-service-usage/.github/.OwlBot.lock.yaml

@@ -1,3 +1,3 @@
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:dfa9b663b32de8b5b327e32c1da665a80de48876558dd58091d8160c60ad7355
+  digest: sha256:ae600f36b6bc972b368367b6f83a1d91ec2c82a4a116b383d67d547c56fe6de3

packages/google-cloud-service-usage/.kokoro/release.sh

@@ -26,7 +26,7 @@ python3 -m pip install --upgrade twine wheel setuptools
 export PYTHONUNBUFFERED=1
 
 # Move into the package, build the distribution and upload.
-TWINE_PASSWORD=$(cat "${KOKORO_GFILE_DIR}/secret_manager/google-cloud-pypi-token")
+TWINE_PASSWORD=$(cat "${KOKORO_KEYSTORE_DIR}/73713_google-cloud-pypi-token-keystore-1")
 cd github/python-service-usage
 python3 setup.py sdist bdist_wheel
 twine upload --username __token__ --password "${TWINE_PASSWORD}" dist/*

packages/google-cloud-service-usage/.kokoro/release/common.cfg

@@ -23,8 +23,18 @@ env_vars: {
     value: "github/python-service-usage/.kokoro/release.sh"
 }
 
+# Fetch PyPI password
+before_action {
+  fetch_keystore {
+    keystore_resource {
+      keystore_config_id: 73713
+      keyname: "google-cloud-pypi-token-keystore-1"
+    }
+  }
+}
+
 # Tokens needed to report release status back to GitHub
 env_vars: {
   key: "SECRET_MANAGER_KEYS"
-  value: "releasetool-publish-reporter-app,releasetool-publish-reporter-googleapis-installation,releasetool-publish-reporter-pem,google-cloud-pypi-token"
+  value: "releasetool-publish-reporter-app,releasetool-publish-reporter-googleapis-installation,releasetool-publish-reporter-pem"
 }