I've been getting this message for almost three weeks now.
I tried refreshing pacman keys but it didn't work.
Folks at IRC told me to report it.

<pre>
:: Starting full system upgrade...
resolving dependencies...
looking for conflicting packages...

Packages (3) parabola-keyring-20170512.1-1 your-freedom-20170525.1-1
your-privacy-20170521-1

Total Download Size: 0.12 MiB
Total Installed Size: 0.23 MiB
Net Upgrade Size: -0.01 MiB

:: Proceed with installation? [Y/n] y
:: Retrieving packages...
parabola-keyring-20... 107.2 KiB 147K/s 00:01 [----------------------] 100%
your-freedom-201705... 15.4 KiB 308K/s 00:00 [----------------------] 100%
your-privacy-201705... 4.6 KiB 1150K/s 00:00 [----------------------] 100%
(3/3) checking keys in keyring [----------------------] 100%
(3/3) checking package integrity [----------------------] 100%
error: parabola-keyring: signature from "Parabola automatic package builder <dev@lists.parabolagnulinux.org>" is marginal trust
:: File /var/cache/pacman/pkg/parabola-keyring-20170512.1-1-any.pkg.tar.xz is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] y
error: your-freedom: signature from "Parabola automatic package builder <dev@lists.parabolagnulinux.org>" is marginal trust
:: File /var/cache/pacman/pkg/your-freedom-20170525.1-1-any.pkg.tar.xz is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] y
error: your-privacy: signature from "Parabola automatic package builder <dev@lists.parabolagnulinux.org>" is marginal trust
:: File /var/cache/pacman/pkg/your-privacy-20170521-1-any.pkg.tar.xz is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] y
error: failed to commit transaction (invalid or corrupted package (PGP signature))
Errors occurred, no packages were upgraded.
</pre>