asynchronous aiohttp requests fails, but synchronous requests succeed

I suspect certificate validation chain is broken on your machine. On Ubuntu everything is working, as @dano mentioned.

Anyway, you may disable ssl validation by creating custom Connector instance:

import asyncio
import aiohttp

urls = [
    'http://www.whitehouse.gov/cea/',
    'http://www.whitehouse.gov/omb',
    'http://www.google.com']


def test_async():
    connector = aiohttp.TCPConnector(verify_ssl=False)
    for url in urls:
        try:
            r = yield from aiohttp.request('get', url, connector=connector)
        except aiohttp.errors.ClientOSError as e:
            print('bad eternal link %s: %s' % (url, e))
        else:
            print(r.status)


if __name__ == '__main__':
    print('async')
    asyncio.get_event_loop().run_until_complete(test_async())

BTW, requests library is shipped with own certificate bundle. Maybe we need to do the same for aiohttp?

UPD. See also https://github.com/aio-libs/aiohttp/issues/341

I had the same problem on an old Linux server with out of date CA root certificates, and loading certifi CA certificate bundle in a SSLContext fixed the issue.

import aiohttp
import ssl
import certifi

ssl_context = ssl.create_default_context(cafile=certifi.where())
async with aiohttp.ClientSession() as session:
    async with session.get('https://some.foo/bar/', ssl=ssl_context) as response:
        print(await response.text())