bug#45198: 28.0.50; Sandbox mode

[Stefan Monnier]

>>  static void
>>  redisplay_internal (void)
>>  {
>> +  /* Not sure if it's important to avoid redisplay inside a sandbox,
>> +     but it seems safer to avoid risking introducing security holes via
>> +     image libraries and such.  */
>> +  ensure_no_sandbox ();
>
> You cannot usefully call error from redisplay.

Hmm... but this is at the entrance to redisplay, so I though it should
still be safe at that point.  If it's a problem we can replace the above
with

    if (emacs_is_sandboxed)
      return;


-- Stefan