Run moto in a separate process so it works on py3

with_moto.py

from contextlib import contextmanager
from multiprocessing import Process, Queue

from moto.server import DomainDispatcherApplication, create_backend_app
from werkzeug.serving import make_server


def server_runner(port_queue: Queue, service: str):
    main_app = DomainDispatcherApplication(create_backend_app, service=service)
    server = make_server(host='localhost', port=0, app=main_app, threaded=True)
    port_queue.put(server.port)
    server.serve_forever()


@contextmanager
def moto_server(service):
    """
    Start a Moto (fake aws) service and yield the port it runs on.
    """
    port_queue = Queue()
    process = Process(target=server_runner, args=(port_queue, service))
    process.start()
    try:
        yield port_queue.get(timeout=5)
    finally:
        process.terminate()