server.py

import base64
from json import dumps

from httplib2 import Http


def hello_pubsub(event, context):
    """Triggered from a message on a Cloud Pub/Sub topic.
    Args:
         event (dict): Event payload.
         context (google.cloud.functions.Context): Metadata for the event.
    """
    pubsub_message = base64.b64decode(event["data"]).decode("utf-8")
    url = "Chat-Channel"
    bot_message = {"text": pubsub_message}

    message_headers = {"Content-Type": "application/json; charset=UTF-8"}

    http_obj = Http()

    response = http_obj.request(
        uri=url,
        method="POST",
        headers=message_headers,
        body=dumps(bot_message),
    )