fix: require python 3.7+ (#768)

* chore(python): drop python 3.6 Source-Link: googleapis/synthtool@4f89b13 Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:e7bb19d47c13839fe8c147e50e02e8b6cf5da8edd1af8b82208cd6f66cc2829c * add api_description to .repo-metadata.json * require python 3.7+ in setup.py * remove python 3.6 sample configs * 🦉 Updates from OwlBot post-processor See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md * exclude templated README * restore manual changes to noxfile.py * update owlbot.py to apply manual changes from #759 * regenerate pb2 files using latest version of grpcio tools Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com> Co-authored-by: Anthonios Partheniou <partheniou@google.com> Co-authored-by: Astha Mohta <35952883+asthamohta@users.noreply.github.com>

Author: 3 people

.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:a5d81b61dfd1a432d3c03f51a25d2e71b37be24da509966d50724aea7c57c5c2
-# created: 2022-07-04T12:33:08.125873124Z
+ digest: sha256:e7bb19d47c13839fe8c147e50e02e8b6cf5da8edd1af8b82208cd6f66cc2829c
+# created: 2022-07-05T18:31:20.838186805Z

.kokoro/samples/python3.6/common.cfg

@@ -13,5 +13,6 @@
  "requires_billing": true,
  "default_version": "v1",
  "codeowner_team": "@googleapis/api-spanner-python",
- "api_shortname": "spanner"
+ "api_shortname": "spanner",
+ "api_description": "is a fully managed, mission-critical, \nrelational database service that offers transactional consistency at global scale, \nschemas, SQL (ANSI 2011 with extensions), and automatic, synchronous replication \nfor high availability.\n\nBe sure to activate the Cloud Spanner API on the Developer's Console to\nuse Cloud Spanner from your project."
 }

.kokoro/samples/python3.6/continuous.cfg

@@ -22,7 +22,7 @@ In order to add a feature:
  documentation.
 
 - The feature must work fully on the following CPython versions:
- 3.6, 3.7, 3.8, 3.9 and 3.10 on both UNIX and Windows.
+ 3.7, 3.8, 3.9 and 3.10 on both UNIX and Windows.
 
 - The feature must not add unnecessary dependencies (where
  "unnecessary" is of course subjective, but new dependencies should
@@ -221,13 +221,11 @@ Supported Python Versions
 
 We support:
 
-- `Python 3.6`_
 - `Python 3.7`_
 - `Python 3.8`_
 - `Python 3.9`_
 - `Python 3.10`_
 
-.. _Python 3.6: https://docs.python.org/3.6/
 .. _Python 3.7: https://docs.python.org/3.7/
 .. _Python 3.8: https://docs.python.org/3.8/
 .. _Python 3.9: https://docs.python.org/3.9/
@@ -239,7 +237,7 @@ Supported versions can be found in our ``noxfile.py`` `config`_.
 .. _config: https://github.com/googleapis/python-spanner/blob/main/noxfile.py
 
 
-We also explicitly decided to support Python 3 beginning with version 3.6.
+We also explicitly decided to support Python 3 beginning with version 3.7.
 Reasons for this include:
 
 - Encouraging use of newest versions of Python 3

.kokoro/samples/python3.6/periodic-head.cfg

@@ -56,12 +56,13 @@ dependencies.
 
 Supported Python Versions
 ^^^^^^^^^^^^^^^^^^^^^^^^^
-Python >= 3.6
+Python >= 3.7
 
 Deprecated Python Versions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 Python == 2.7.
 Python == 3.5.
+Python == 3.6.
 
 
 Mac/Linux