This line has been in here since Coco, and I can't see any reason why it
should be kept. Can you?

This is an ugly hack, but it fixes the issue where the REPL will
sometimes stop responding to arrow keys after an error has been thrown
in user code. Turns out, this happens whenever a string (or anything
other than something with Error in its prototype hierarchy) is thrown.
The fix is to restore "raw mode" on the input TTY handle when this
situation is detected, by the time-honored method of turning it off and
on again.