List in-flight connections #561

AsyncConnectionPool.aclose() raises RuntimeError: The connection pool was closed while 1 HTTP requests/responses were still in-flight. if there are any on-going requests.

It would be nice to provide a list of URLs to help me understand what I'm doing wrong. At the moment I'm adding print statements to the httpcore code to figure this out.

Something like this would be nice:

RuntimeError: The connection pool was closed while 3 HTTP requests/responses were still in-flight:
URL(scheme=b'https', host=b'www.example.com', port=None, target=b'/foo')
URL(scheme=b'https', host=b'www.example.com', port=None, target=b'/bar')
URL(scheme=b'https', host=b'www.example.net', port=None, target=b'/baz')