Drop older asyncio workarounds for Python < 3.7

[pepoluan]

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Since we've dropped 3.6, and 3.7 has A LOT of asyncio improvements (here's a glance of some -- already a long list!), we might want to start replacing all 'workarounds' that catered to Python < 3.7 to things that are 'more elegant' (and definitely more up-to-date).

Not marking this for any particular version. But definitely making this a tech-debt.

[pepoluan]

When PR #359 gets merged, we will have completely removed any support for Python<3.7, and this issue can go forward.

Edit/update: That PR has been merged, there's no stopping us now from going 'modern' 😉