chore(python): fix prerelease session [autoapprove] (#1090)

Source-Link: googleapis/synthtool@1b9ad76
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:9db98b055a7f8bd82351238ccaacfd3cda58cdf73012ab58b8da146368330021

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

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:bc5eed3804aec2f05fad42aacf973821d9500c174015341f721a984a0825b6fd
-# created: 2022-04-21T15:43:16.246106921Z
+  digest: sha256:9db98b055a7f8bd82351238ccaacfd3cda58cdf73012ab58b8da146368330021
+# created: 2022-07-25T16:02:49.174178716Z

.kokoro/continuous/prerelease-deps.cfg

@@ -0,0 +1,7 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Only run this nox session.
+env_vars: {
+    key: "NOX_SESSION"
+    value: "prerelease_deps"
+}

.kokoro/presubmit/prerelease-deps.cfg

@@ -0,0 +1,7 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Only run this nox session.
+env_vars: {
+    key: "NOX_SESSION"
+    value: "prerelease_deps"
+}

.kokoro/test-samples-impl.sh

@@ -33,7 +33,7 @@ export PYTHONUNBUFFERED=1
 env | grep KOKORO
 
 # Install nox
-python3.6 -m pip install --upgrade --quiet nox
+python3.9 -m pip install --upgrade --quiet nox
 
 # Use secrets acessor service account to get secrets
 if [[ -f "${KOKORO_GFILE_DIR}/secrets_viewer_service_account.json" ]]; then
@@ -76,7 +76,7 @@ for file in samples/**/requirements.txt; do
     echo "------------------------------------------------------------"
 
     # Use nox to execute the tests for the project.
-    python3.6 -m nox -s "$RUN_TESTS_SESSION"
+    python3.9 -m nox -s "$RUN_TESTS_SESSION"
     EXIT=$?
 
     # If this is a periodic build, send the test log to the FlakyBot.