After upgrading to Python 3.8, users of sshuttle report seeing this error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "assembler.py", line 38, in <module>
  File "sshuttle.server", line 298, in main
  File "/usr/lib/python3.8/socket.py", line 544, in fromfd
    return socket(family, type, proto, nfd)
  File "/usr/lib/python3.8/socket.py", line 231, in __init__
    _socket.socket.__init__(self, family, type, proto, fileno)
OSError: [Errno 88] Socket operation on non-socket

https://github.com/sshuttle/sshuttle/issues/381

The cause of the error is this line: 
https://github.com/sshuttle/sshuttle/blob/6ad4473c87511bcafaec3d8d0c69dfcb166b48ed/sshuttle/server.py#L297 which does:

socket.fromfd(sys.stdin.fileno(), socket.AF_INET, socket.SOCK_STREAM)
socket.fromfd(sys.stdout.fileno(), socket.AF_INET, socket.SOCK_STREAM)

Where sys.stdin and sys.stdout are stdin/stdout provided by the ssh server when it ran our remote ssh process.

I believe this change in behavior is as a result of a fix for the following bug: https://bugs.python.org/issue35415

I am wondering if this is a bug in Python for causing such a regression, or a bug in sshuttle. Possibly sshuttle is using socket.fromfd in a way that was never intended?

Would appreciate an authoritative answer on this.

Thanks