v3.15.0a3
gh-85524: Raise "UnsupportedOperation" on FileIO.readall (#141214)
gh-141376: Fix exported symbols (GH-141377)
gh-141311: Avoid assertion in BytesIO.readinto() (GH-141333)
gh-60107: Remove a copy from RawIOBase.read (#141532)
gh-142594: fix by property calls io.TextIOWrapper.detach (GH-142706)