[Assist] "X Y" is unknown trust, parabola-keyring does not help

[Rudolf Dovičín]

I cannot actualise my computer with Parabola.
(I had actualised it many times before without problems.)

First command
# pacman -Syu

gived me cca 80 packages to actualise, I saw archlinux-keyring between them,
so I broke full actualisation and tried separately first:
# pacman -Sy archlinux-keyring

Next command
# pacman -Syu

gives me errors:
error: linux-libre-api-headers: signature from "André Silva
<emulatorman at riseup.net>" is unknown trust
:: File /var/cache/pacman/pkg/linux-libre-api-headers-4.0_gnu-1-x86_64.pkg.tar.xz
is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] n
error: iceweasel: signature from "André Silva
<emulatorman at riseup.net>" is unknown trust
:: File /var/cache/pacman/pkg/iceweasel-1:38.0.1.deb5-1-x86_64.pkg.tar.xz
is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] n
error: mesa-libcl: signature from "André Silva
<emulatorman at riseup.net>" is unknown trust
:: File /var/cache/pacman/pkg/mesa-libcl-10.5.6-1-x86_64.pkg.tar.xz is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] n
error: linux-libre: signature from "André Silva
<emulatorman at riseup.net>" is unknown trust
:: File /var/cache/pacman/pkg/linux-libre-4.0.4_gnu-2-x86_64.pkg.tar.xz
is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] n
error: pacman-mirrorlist: signature from "André Silva
<emulatorman at riseup.net>" is unknown trust
:: File /var/cache/pacman/pkg/pacman-mirrorlist-20150530-1.parabola1-any.pkg.tar.xz
is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] n
error: texlive-bin: signature from "André Silva
<emulatorman at riseup.net>" is unknown trust
:: File /var/cache/pacman/pkg/texlive-bin-2014.34260-8.parabola1-x86_64.pkg.tar.xz
is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] n

(It seem to me that other signatures does not gives such error.)

What can be wrong? (And how can I try to solve it?)

Best regards:
-- 
Rudolf Dovičín
Partizánska 1506/92-34
957 01  Bánovce nad Bebravou 1
SLOVENSKO
xmpp: ruwolf at jabbim.sk
(cellular: +421 940 872 846, short messages only)