chore(spanner): release 1.13.0 (#9731)

* chore(spanner): release 1.13.0

* address PR comments

CHANGELOG.md

@@ -4,6 +4,22 @@
 
 [1]: https://pypi.org/project/google-cloud-spanner/#history
 
+## 1.13.0
+
+11-11-2019 15:59 PST
+
+
+### Implementation Changes
+Fix TransactionPingingPool to stop thowing ''NoneType' object is not callable' error. ([#9609](https://github.com/googleapis/google-cloud-python/pull/9609))
+Return sessions from pool in LIFO order. ([#9454](https://github.com/googleapis/google-cloud-python/pull/9454))
+
+### Documentation
+- Add Python 2 sunset banner to documentation. ([#9036](https://github.com/googleapis/google-cloud-python/pull/9036))
+- Update description of the `timeout_secs` parameter. ([#9381](https://github.com/googleapis/google-cloud-python/pull/9381))
+
+### Internal / Testing Changes
+- Harden `test_transaction_batch_update*` systests against partial success + abort. ([#9579](https://github.com/googleapis/google-cloud-python/pull/9579))
+
 ## 1.12.0
 
 10-23-2019 19:09 PDT

setup.py

@@ -22,7 +22,7 @@
 
 name = "google-cloud-spanner"
 description = "Cloud Spanner API client library"
-version = "1.12.0"
+version = "1.13.0"
 # Should be one of:
 # 'Development Status :: 3 - Alpha'
 # 'Development Status :: 4 - Beta'