Deliver a Drive file when someone buys on Stripe

import stripe
from clickruntime import on_event, credentials, verify, notify
from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build

FILES = {"price_ebook": "1AbCdEbookFileId", "price_templates": "1XyZTemplatesFileId"}

@on_event
def handle(event):
    if not verify.stripe(event.body, event.header("Stripe-Signature"), credentials.secret("STRIPE_WEBHOOK_SECRET")):
        return {"ignored": "bad signature"}
    if event.json["type"] != "checkout.session.completed":
        return {"ignored": event.json["type"]}
    session = event.json["data"]["object"]
    email = session["customer_details"]["email"]
    stripe.api_key = credentials.secret("STRIPE_API_KEY")
    drive = build("drive", "v3", credentials=Credentials(credentials.connection("google", "work")), cache_discovery=False)
    shared = []
    for item in stripe.checkout.Session.list_line_items(session["id"]).data:
        file_id = FILES.get(item.price.id)
        if file_id:
            drive.permissions().create(fileId=file_id, sendNotificationEmail=True,
                                       emailMessage="Thanks for your purchase! Here is your download.",
                                       body={"type": "user", "role": "reader", "emailAddress": email}).execute()
            shared.append(item.description)
    notify.email_me(f"Delivered to {email}", ", ".join(shared) or "No matching file for this checkout")
    return {"shared": shared}