[windows][python3.8][asyncio][aiohttp] Event loop is closed

[GuillaumeDSM]

This is a Windows only issue. Since Python3.8, the Windows loop default implementation generates issues with several libs including aiohttp.

To avoid this warning, SelectorEventLoop (see event_loop doc) is forced in

• OctoBot-Trading tests (https://github.com/Drakkar-Software/OctoBot-Trading/pull/393)
• OctoBot-Tentacles-Manager tests (https://github.com/Drakkar-Software/OctoBot-Tentacles-Manager/pull/71)

fix from https://github.com/encode/httpx/issues/914#issuecomment-622586610

This warning also sometime appears during the bot run (ex: after a data collector run). Is currently accepted and only visible in console logs. For now no fix is available.

Todo: Use fixed versions of python or aiohttp and revert SelectorEventLoop force is tests.