Bad error message if I forget to return from a page handler

[ShermanGirl]

Maybe print the exception and return 500 or 404?

@app.route('/')
async def index(r):
    pass

Exception in callback <built-in method task_done of protocol.Protocol object at 0x2b6d770>
handle: <Handle Protocol.task_done>
ValueError: Page handler did not return a string

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "uvloop/cbhandles.pyx", line 49, in uvloop.loop.Handle._run
SystemError: <built-in method write of uvloop.loop.TCPTransport object at 0x2a2d928> returned a result with an error set

[MarkReedZ]

We were setting the exception before sending back the 500 response to the client so we complained when the transport object returned successfully. Now it just looks like this:

Exception in callback <built-in method task_done of protocol.Protocol object at 0x2b6d770>
handle: <Handle Protocol.task_done>
ValueError: Page handler did not return a string

Leaving this issue open to review later. I'd like to just raise the exception without seeing the callback and handle lines. Also the ValueError should probably be a custom exception.

[MarkReedZ]

Closing this. The exception remains as above which I think is fine.