[python-tulip] Tulip unit tests: use asyncio module, not submodules

[Victor Stinner]

Hi,

I don't understand why Tulip unit tests import submodules instead of
using the public API. Example: "from asyncio import tasks" and then
use "tasks.Task()".

What do you think of only importing asyncio and use the asyncio module instead?

It would ensure that all required symbols are exported. For example,
SubprocessTransport was not exported in a previous version.

Victor