control_server in pubsub-thermostat example produces a "No handlers could be found for logger" error/warning

[handcyclist]

The control_server.py works but produces the following error/warning after the first temperature message is received, then the error/warning does not appear again. The error/warning is:

No handlers could be found for logger "google.cloud.pubsub_v1.subscriber._protocol.streaming_pull_manager"

The same message, but with pubsub, not pubsub_v1 had been appearing for a while, but the message with pubsub_v1 started appearing after the last time I upgraded using "pip install --upgrade [some modules] as per the md instructions" (about 2018Jun12)