See googleapis/gapic-generator-python#2385 where test test_async_unary_stream_reader[rest_asyncio] fails with 2.40.0 but succeeds with older versions. This only happens when using async rest transport, and when debug logging is enabled. This specific feature was added in #1678.

I believe the problem is that 2.40.0 introduced await response.json() shown below

My initial thought is that if await response.json() is called in google-auth, then there is no response to await on the client side. We should remove response_log_async to avoid introducing a breaking change (and to allow responses to be read in client code, rather than in google-auth). We then would need to figure out how to log the async responses without introducing a change in behavior on the client side.