[New-bugs-announce] [issue36294] `io.BufferedIOBase` returns `None`

[Cyker Way]

New submission from Cyker Way <cykerway at gmail.com>:

Document of [BufferedIOBase](https://docs.python.org/3/library/io.html#io.BufferedIOBase) says:

>   ...unlike their RawIOBase counterparts, they will never return None.

But this example shows the above statement is not true:

    import io
    import os
    import sys

    os.set_blocking(sys.stdin.fileno(), False)
    print(isinstance(sys.stdin.buffer, io.BufferedIOBase))
    print(sys.stdin.buffer.read())

Output:

    True
    None

----------
components: IO, Library (Lib)
messages: 337941
nosy: cykerway
priority: normal
severity: normal
status: open
title: `io.BufferedIOBase` returns `None`
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue36294>
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