chore(python): simplify nox steps in CONTRIBUTING.rst (#195)

Source-Link: googleapis/synthtool@26558ba
Post-Processor: gcr.io/repo-automation-bots/owlbot-python:latest@sha256:99d90d097e4a4710cc8658ee0b5b963f4426d0e424819787c3ac1405c9a26719

chore: add kokoro 3.9 config templates
chore: update precommit hook pre-commit/pre-commit-hooks to v4
chore(python): remove hardcoded versions in CONTRIBUTING.rst
docs: omit mention of Python 2.7 in 'CONTRIBUTING.rst'

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -1,3 +1,3 @@
 docker:
   image: gcr.io/repo-automation-bots/owlbot-python:latest
-  digest: sha256:58c7342b0bccf85028100adaa3d856cb4a871c22ca9c01960d996e66c40548ce
+  digest: sha256:99d90d097e4a4710cc8658ee0b5b963f4426d0e424819787c3ac1405c9a26719

.kokoro/samples/python3.9/common.cfg

@@ -0,0 +1,40 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Build logs will be here
+action {
+  define_artifacts {
+    regex: "**/*sponge_log.xml"
+  }
+}
+
+# Specify which tests to run
+env_vars: {
+    key: "RUN_TESTS_SESSION"
+    value: "py-3.9"
+}
+
+# Declare build specific Cloud project.
+env_vars: {
+    key: "BUILD_SPECIFIC_GCLOUD_PROJECT"
+    value: "python-docs-samples-tests-py39"
+}
+
+env_vars: {
+    key: "TRAMPOLINE_BUILD_FILE"
+    value: "github/python-bigquery-sqlalchemy/.kokoro/test-samples.sh"
+}
+
+# Configure the docker image for kokoro-trampoline.
+env_vars: {
+    key: "TRAMPOLINE_IMAGE"
+    value: "gcr.io/cloud-devrel-kokoro-resources/python-samples-testing-docker"
+}
+
+# Download secrets for samples
+gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/python-docs-samples"
+
+# Download trampoline resources.
+gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/trampoline"
+
+# Use the trampoline script to run in docker.
+build_file: "python-bigquery-sqlalchemy/.kokoro/trampoline.sh"

.kokoro/samples/python3.9/continuous.cfg

@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}

.kokoro/samples/python3.9/periodic-head.cfg

@@ -0,0 +1,11 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}
+
+env_vars: {
+    key: "TRAMPOLINE_BUILD_FILE"
+    value: "github/python-pubsub/.kokoro/test-samples-against-head.sh"
+}

.kokoro/samples/python3.9/periodic.cfg

@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "False"
+}

.kokoro/samples/python3.9/presubmit.cfg

@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}

.pre-commit-config.yaml

@@ -16,7 +16,7 @@
 # See https://pre-commit.com/hooks.html for more hooks
 repos:
 -   repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v3.4.0
+    rev: v4.0.1
     hooks:
     -   id: trailing-whitespace
     -   id: end-of-file-fixer

CONTRIBUTING.rst

@@ -68,15 +68,12 @@ Using ``nox``
 We use `nox <https://nox.readthedocs.io/en/latest/>`__ to instrument our tests.
 
 - To test your changes, run unit tests with ``nox``::
+    $ nox -s unit
 
-    $ nox -s unit-2.7
-    $ nox -s unit-3.8
-    $ ...
+- To run a single unit test::
 
-- Args to pytest can be passed through the nox command separated by a `--`. For
-  example, to run a single test::
+    $ nox -s unit-3.9 -- -k <name of test>
 
-    $ nox -s unit-3.8 -- -k <name of test>
 
   .. note::
 
@@ -143,18 +140,16 @@ Running System Tests
 - To run system tests, you can execute::
 
    # Run all system tests
-   $ nox -s system-3.8
-   $ nox -s system-2.7
+   $ nox -s system
 
    # Run a single system test
-   $ nox -s system-3.8 -- -k <name of test>
+   $ nox -s system-3.9 -- -k <name of test>
 
 
   .. note::
 
-      System tests are only configured to run under Python 2.7 and
-      Python 3.8. For expediency, we do not run them in older versions
-      of Python 3.
+      System tests are only configured to run under Python 3.8 and 3.9.
+      For expediency, we do not run them in older versions of Python 3.
 
   This alone will not run the tests. You'll need to change some local
   auth settings and change some configuration in your project to
@@ -218,8 +213,8 @@ Supported versions can be found in our ``noxfile.py`` `config`_.
 .. _config: https://github.com/googleapis/python-bigquery-sqlalchemy/blob/master/noxfile.py
 
 
-We also explicitly decided to support Python 3 beginning with version
-3.6. Reasons for this include:
+We also explicitly decided to support Python 3 beginning with version 3.6.
+Reasons for this include:
 
 -  Encouraging use of newest versions of Python 3
 -  Taking the lead of `prominent`_ open-source `projects`_