Has anyone else had trouble publishing to a pubsub topic from within a cloud function?

I have deployed a cloud function something along the lines of:

from google.cloud import pubsub

def pubsub_handler(message):
    client = pubsub.PublisherClient()
    topic = 'projects/TEST-PROJECT/topics/TEST-TOPIC'
    client.publish(topic=topic, data='', test_param='test')

handle_pubsub_event(pubsub_handler)

and when I invoke the function and look at the logs, I see the following error:

Exception in 'grpc._cython.cygrpc.ssl_roots_override_callback' ignored E0424 15:48:44.194749483 17 security_connector.cc:1170] assertion failed: pem_root_certs != nullptr

I am using Python 2.7