unittest.mock.patch does not work on WASM build

[treyhunner]

Bug report

When importing unittest.mock, an exception is raised due to unittest.mock importing asyncio.

It seems the asyncio library is only used in unittest.mock when mocking async functions.

I believe delaying the import of asyncio until the moment it's needed would make unittest.mock functional for most use cases on WASM builds.

A demonstration of the error: https://www.pythonmorsels.com/r/35fv2/

Your environment

CPython 3.11.0rc1 built with Emscripten for the web browser

[treyhunner]

Duplicate of #96883. I accidentally opened this issue twice.