Fix #554
In this case, we don't need finally at all.

            if pty.iseof():
                try:
                    client.send(b'')
                except socket.error:
                    pass
                break

If there is no exception, the break will be executed.
Else if the exception is socket.error or child, then the break will be executed.
Else if the exception is Exception or a child, it will be caught by except Exception as e: and a break will be executed there.
Else function is stop now.

Thus, the behavior is equivalent to the old one.