Major Description
Recently the aiohttp transport layer was introduced. This uses an event loop.
The transport layer cleans up when close is called on it, however in some cases, a user may not call close, due to exceptions in their code, or improper usage.
In this case, the user will get an error message saying 'Unclosed client session' and a stack trace that shows aiohttp trying to shutdown and expecting things to be closed but they are left open. aiohttp then cleans this up under the hood, but we should be closing things down properly in advance.