Misleading pyrepl warnings when _curses module is missing

[itamaro]

Bug report

Bug description:

If I run 3.14 on Linux without a working _curses extension, I get this misleading warning from pyrepl:

warning: can't use pyrepl: Windows only

I suspect pyrepl is not actually Windows only, and indeed if I fix _curses it works again.

Presumably, a better warning would be

warning: can't use pyrepl: No module named '_curses'

or something like that

CPython versions tested on:

3.14

Operating systems tested on:

Linux

[sobolevn]

Seems related to #131189