v3.15.0a6
gh-85524: Raise "UnsupportedOperation" on FileIO.readall (#141214)
gh-141376: Fix exported symbols (GH-141377)
gh-144380: Fix incorrect type check in `buffered_iternext()` (#144381)
gh-143378: Fix use-after-free when BytesIO is concurrently mutated during write operations (GH-143408)
gh-60107: Remove a copy from RawIOBase.read (#141532)
gh-142594: fix by property calls io.TextIOWrapper.detach (GH-142706)