pycompat: fix bytestr(bytes) in Python 3.11 In Python 3.10, the `bytes` type itself does not have a `__bytes__` attribute, but it does in 3.11. Yet `bytes(bytes)` does not give the wished output, so we have to add an exceptional case. The added case in the doctest reproduces the problem with Python 3.11. Impact: error treatment in expressions such as `repo[b'invalid']` gets broken.