Asynchronous classmethod handlers not recognized as coroutines if wrapped in functools.partial

[vladmunteanu]

starlette/starlette/routing.py

Line 38 in e430706

if sys.version_info < (3, 8): # pragma: no cover

Although the recent 0.14.0 version adds support for functools.partial for Python 3.6 and Python 3.7, that support appears to be incomplete, not working for classmethods in Python 3.8.

I was unaware of the fact that inspect.iscoroutinefunction does not properly detect a functools.partial as async if it wraps an async classmethod.

TLDR: the previous PR was too cautious, we can always unwrap the functools.partial object to be sure we check the underlying object.

[JayH5]

I'm not certain it's relevant but linking to this suggested change in cPython: python/cpython#16600