chore: fix kokoro config for samples (#426)

Source-Link: googleapis/synthtool@dd05f9d
Post-Processor: gcr.io/repo-automation-bots/owlbot-python:latest@sha256:aea14a583128771ae8aefa364e1652f3c56070168ef31beb203534222d842b8b

Author: gcf-owl-bot[bot]

packages/google-cloud-spanner/.github/.OwlBot.lock.yaml

@@ -1,3 +1,3 @@
 docker:
   image: gcr.io/repo-automation-bots/owlbot-python:latest
-  digest: sha256:5ff7446edeaede81c3ed58b23a4e76a5403fba1350ce28478045657303b6479d
+  digest: sha256:aea14a583128771ae8aefa364e1652f3c56070168ef31beb203534222d842b8b

packages/google-cloud-spanner/.kokoro/samples/python3.6/periodic-head.cfg

@@ -7,5 +7,5 @@ env_vars: {
 
 env_vars: {
     key: "TRAMPOLINE_BUILD_FILE"
-    value: "github/python-pubsub/.kokoro/test-samples-against-head.sh"
+    value: "github/python-spanner/.kokoro/test-samples-against-head.sh"
 }

packages/google-cloud-spanner/.kokoro/samples/python3.7/periodic-head.cfg

@@ -7,5 +7,5 @@ env_vars: {
 
 env_vars: {
     key: "TRAMPOLINE_BUILD_FILE"
-    value: "github/python-pubsub/.kokoro/test-samples-against-head.sh"
+    value: "github/python-spanner/.kokoro/test-samples-against-head.sh"
 }

packages/google-cloud-spanner/.kokoro/samples/python3.8/periodic-head.cfg

@@ -7,5 +7,5 @@ env_vars: {
 
 env_vars: {
     key: "TRAMPOLINE_BUILD_FILE"
-    value: "github/python-pubsub/.kokoro/test-samples-against-head.sh"
+    value: "github/python-spanner/.kokoro/test-samples-against-head.sh"
 }

packages/google-cloud-spanner/.kokoro/samples/python3.9/periodic-head.cfg

@@ -7,5 +7,5 @@ env_vars: {
 
 env_vars: {
     key: "TRAMPOLINE_BUILD_FILE"
-    value: "github/python-pubsub/.kokoro/test-samples-against-head.sh"
+    value: "github/python-spanner/.kokoro/test-samples-against-head.sh"
 }

packages/google-cloud-spanner/CONTRIBUTING.rst

@@ -177,6 +177,30 @@ Build the docs via:
 
    $ nox -s docs
 
+*************************
+Samples and code snippets
+*************************
+
+Code samples and snippets live in the `samples/` catalogue. Feel free to
+provide more examples, but make sure to write tests for those examples.
+Each folder containing example code requires its own `noxfile.py` script
+which automates testing. If you decide to create a new folder, you can
+base it on the `samples/samples` folder (providing `noxfile.py` and
+the requirements files).
+
+The tests will run against a real Google Cloud Project, so you should
+configure them just like the System Tests.
+
+- To run sample tests, you can execute::
+
+   # Run all tests in a folder
+   $ cd samples/samples
+   $ nox -s py-3.8
+
+   # Run a single sample test
+   $ cd samples/samples
+   $ nox -s py-3.8 -- -k <name of test>
+
 ********************************************
 Note About ``README`` as it pertains to PyPI
 ********************************************

packages/google-cloud-spanner/owlbot.py

@@ -121,6 +121,9 @@ def get_staging_dirs(
     "\n\g<0>",
 )
 
+# Update samples folder in CONTRIBUTING.rst
+s.replace("CONTRIBUTING.rst", "samples/snippets", "samples/samples")
+
 # ----------------------------------------------------------------------------
 # Samples templates
 # ----------------------------------------------------------------------------

packages/google-cloud-spanner/samples/samples/noxfile.py

@@ -28,8 +28,9 @@
 # WARNING - WARNING - WARNING - WARNING - WARNING
 # WARNING - WARNING - WARNING - WARNING - WARNING
 
-# Copy `noxfile_config.py` to your directory and modify it instead.
+BLACK_VERSION = "black==19.10b0"
 
+# Copy `noxfile_config.py` to your directory and modify it instead.
 
 # `TEST_CONFIG` dict is a configuration hook that allows users to
 # modify the test configurations. The values here should be in sync
@@ -159,7 +160,7 @@ def lint(session: nox.sessions.Session) -> None:
 
 @nox.session
 def blacken(session: nox.sessions.Session) -> None:
-    session.install("black")
+    session.install(BLACK_VERSION)
     python_files = [path for path in os.listdir(".") if path.endswith(".py")]
 
     session.run("black", *python_files)