example server and client to reproduce a Reason-Phrase bug in Python’s aiohttp library (https://github.com/aio-libs/aiohttp/issues/3532)

example_client.py

import asyncio
from urllib.parse import urljoin

from aiohttp.client import request


async def main():
    for endpoint in ["/success_without_reason", "/failure_without_reason"]:
        async with request("get", urljoin("http://0.0.0.0:8080",
                                          endpoint)) as resp:
            resp.raise_for_status()
            print(f"{endpoint} passes ok")


asyncio.get_event_loop().run_until_complete(main())

example_srv.py

from aiohttp import web

async def success_without_reason(request):
    return web.Response(body="everything is ok", status=200, reason="")

async def failure_without_reason(request):
    return web.Response(body="my tummy feels funny", status=500, reason="")

def init():
    app = web.Application()
    app.router.add_get("/success_without_reason", success_without_reason)
    app.router.add_get("/failure_without_reason", failure_without_reason)
    return app

web.run_app(init())