The Google Cloud client libraries [1] are fully supported. You can use these to access services like Datastore, Spanner, Natural Language, and many other Cloud services. They work on this new runtime, on the flexible environment, on a VM, your local machine, etc. In my opinion, this is the most Pythonic way to integrate Cloud services in your app while maintaining portability.
[1] https://github.com/GoogleCloudPlatform/google-cloud-python -- small caveat, the repo currently states that they're not supported on App Engine standard environment. That will be updated soon to clarify that the Python 3.7 runtime on the standard environment is supported.
[1] https://github.com/GoogleCloudPlatform/google-cloud-python -- small caveat, the repo currently states that they're not supported on App Engine standard environment. That will be updated soon to clarify that the Python 3.7 runtime on the standard environment is supported.