Strange behavior during error recovery

[Karl Berry]

Hi Enrico,

    \s^^?E

I have seen \batchmode fail to exit before, so I'm not sure that
behavior is unexpected. But I'll check. I see no possibility of changing
the messages at this late date, nor is it clear to me what they could be
changed to.

    I get no segmentation fault, like the poster at
    https://tex.stackexchange.com/q/551313/4427

A seg fault is clearly a bug somewhere, but I don't get a seg fault with
the x86_64-linux binary (past or present). I'll ask Dick. --thanks, karl.