Replace asyncio.iscoroutinefunction with inspect.iscoroutinefunction

[hroncok]

DeprecationWarning: 'asyncio.iscoroutinefunction' is deprecated and slated for removal in Python 3.16; use inspect.iscoroutinefunction() instead

Fixes #468

[hroncok]

I still see the warning here when I run tox -e py314 because of pytest-asyncio. It is fixed there in pytest-dev/pytest-asyncio@d043698 but not yet released.

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Also, about the CI failure... no idea what it means.

[nicoddemus]

Hmm that's strange indeed, might be something temporary? Will try to restart CI a bit later to see if it goes away.

[webknjaz]

@seifertm could you make a release if pytest-asyncio? Other plugins like pytest-mock start testing against Python 3.14 and hit that warning fixed in the main branch.

[nicoddemus]

The failure is something related to hynek/build-and-inspect-python-package, because we are having the same error in #466, which ran fine two weeks ago.

[nicoddemus]

@hroncok rebased on main, which fixed the build-and-check-package problem.

[nicoddemus]

Thanks @hroncok!