Resolve KeyError exception when calling unsupported request method

[attie]

What do these changes do?

When using a web.View class, and querying with an unsupported request method (e.g: class implements GET, client queries with POST), the client would receive an "Empty Reply" from the server, and the server would log a KeyError exception.

This patch resolves the issue, and permits the partially prepared 405 response through to the client.

I'm not sure if this abides by the CORS rules, but it's certainly better than an exception and no response.

Are there changes in behavior for the user?

No changes required.

Related issue number

• Fix 'Method Not Allowed' on class based views #178 - after applying this fix, the KeyError and "Empty Reply" are still present.
• method '*' treated differently from others #241 - possibly

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes (N/A)
• Add a new news fragment into the CHANGES folder

Tests

I'm not sure how to go about testing this fix, but I have provided a demo application and curl comamnd to demonstrate it below.

from aiohttp import web
import aiohttp_cors

router = web.RouteTableDef()

@router.view('/ping')
class Ping(web.View, aiohttp_cors.CorsViewMixin):
    async def get(self):
        return web.Response(status=200, text='pong')

app = web.Application()
app.add_routes(router)

cors_defaults = {
    '*': aiohttp_cors.ResourceOptions(
        max_age = 3600,
        allow_methods = '*',
        allow_headers = '*',
        expose_headers = '*',
        allow_credentials = True,
    )
}
cors = aiohttp_cors.setup(app, defaults=cors_defaults)

for route in app.router.routes():
    cors.add(route)

web.run_app(app, port=8080)

curl -D- http://localhost:8080/ping
curl -D- -XPOST http://localhost:8080/ping

[attie]

Please ignore this pull request in favour of #178...

I thought I still had that patch applied, but I didn't.