ClientConnectorError：无法连接到主机httpbin.org:80 ssl：False [getaddrinfo failed]

Question

我尝试发出异步请求来获取URL（Windows 7上的Anaconda Python 3.6.3 64位）

import asyncio
from aiohttp import ClientSession

async def hello(url):
    async with ClientSession() as session:
        async with session.get(url) as response:
            response = await response.read()
            print(response)

loop = asyncio.get_event_loop()

loop.run_until_complete(hello("http://httpbin.org/headers"))

（来自this article的代码）

但是我收到以下错误：

Traceback (most recent call last):

  File "<ipython-input-89-ff1fbb8cc713>", line 1, in <module>
    runfile('C:/Users/me/Code/async_fetch.py', wdir='C:/Users/me/Code/')

  File "C:\App\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 710, in runfile
    execfile(filename, namespace)

  File "C:\App\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 101, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "C:/Users/me/Code/async_fetch.py", line 19, in <module>
    loop.run_until_complete(hello("http://httpbin.org/headers"))

  File "C:\APP\Anaconda3\envs\dashboards\lib\asyncio\base_events.py", line 467, in run_until_complete
    return future.result()

  File "C:/Users/me/Code/async_fetch.py", line 13, in hello
    async with session.get(url) as response:

  File "C:\App\Anaconda3\lib\site-packages\aiohttp\client.py", line 783, in __aenter__
    self._resp = await self._coro

  File "C:\App\Anaconda3\lib\site-packages\aiohttp\client.py", line 320, in _request
    traces=traces

  File "C:\App\Anaconda3\lib\site-packages\aiohttp\connector.py", line 418, in connect
    traces=traces

  File "C:\App\Anaconda3\lib\site-packages\aiohttp\connector.py", line 733, in _create_connection
    traces=traces

  File "C:\App\Anaconda3\lib\site-packages\aiohttp\connector.py", line 823, in _create_direct_connection
    raise ClientConnectorError(req.connection_key, exc) from exc

ClientConnectorError: Cannot connect to host httpbin.org:80 ssl:False [getaddrinfo failed]