bug#55568: (no subject)

We discussed this again on IRC yesterday, see logs here:
https://logs.guix.gnu.org/guile/2022-09-21.log#120814

We realised that the *real* underlying issue is that false-if-exception
is not working in the context of my test code, i.e. when another
exception handler is set up.  See further info here:
https://issues.guix.gnu.org/57095#5

It would still be possible to work around the immediate issue by
modifying terminal-width to check the return value of getenv instead of
catching the exception in string->number.  However the underlying issue
will be difficult to solve.