bug#40248: 27.0.90; Failure open .authinfo.gpg from Gnus

[Robert Pluim]

>>>>> On Mon, 30 Mar 2020 16:10:15 +0300, Eli Zaretskii <eliz@gnu.org> said:
    Eli> If you can find those cases where you saw non-ASCII data in this case,
    Eli> by all means describe them or point to relevant discussions.
    >> 
    >> My (admittedly fallible) memory is that gpg always uses UTF-8 for
    >> non-ASCII data (except for some old versions that %-escape it instead).

    Eli> Is that true even on MS-Windows?  can someone please verify that?  If
    Eli> gpg uses UTF-8 on all platforms, the 'undecided' isn't TRT, as in some
    Eli> cases Emacs could mistakenly decide the encoding is the current system
    Eli> codepage.  We should use 'utf-8' instead if UTF-8 is guaranteed.

Having now re-checked it, I was wrong. gpg uses UTF-8 consistenly
_internally_, but converts to/from whatever it thinks the native
codepage is (on MS-Windows and unixy platforms).

Robert