bug#12923: 24.2; epa-file--find-file-not-found-function: Opening input file: Can't decrypt, Exit

[Stefan Monnier]

> If the above magic works well for typical use-cases, it might be worth
> adding them to Emacs too.

I took this bug-report to say "make sure that we handle .gpg files in
a file-safe way, showing the raw-bytes if we can't show the decrypted
content".  So rather than try to detect that we have a keyring, we
should just try to decrypt and look at the resulting error
(which should hopefully be different for "bad decryption key" than it
is for "trying to decrypt something else (e.g. a keyring file)").


        Stefan