versions of mutt/neomutt (in response to https://gitlab.com/muttmua/mutt/issues/39) don't work with old gpg. (There's an alternative workaround, "unset pgp_check_gpg_decrypt_status_fd", but this is still subject to the issue reported in the above gitlab ticket where unencrypted messages may be reported as encrypted). Prompted by a report from stsp@.