Test failures and DeprecationWarnings in Python 3.8

[tirkarthi]

There are test case failures in Python 3.8 . I think this is due to mocking create_server which is now AsyncMock instead of MagicMock with changes in https://bugs.python.org/issue26467 where coroutines when patched return AsyncMock. Thus there are warnings due to the mock not being awaited. The old behavior can be used with MagicMock explicitly passed while patching. There also seems to be a bug that AsyncMock is not recording call_args and other values for synchronous API.

There is also DeprecationWarning since StreamReader and StreamWriter are merged into Stream class in https://bugs.python.org/issue36889. Attached is a log with 3.9.0a0 but these are reproducible on 3.8.0b1 as well.

aiosmptd.log

[waynew]

There's also PendingDeprecationWarning: Task.all_tasks() is deprecated, use asyncio.all_tasks() instead

[pepoluan]

This will be irrelevant when #192 is merged because that PR took out the whole suite of test cases that caused these warnings. See commit 7b3049f

So for now I'm labeling this as wontfix