[Assist] pacstrap spews a dozen "(invalid or corrupted package (PGP signature))" errors on fresh install

[Seth]

Environment:

Virtualbox x64 VM
Parabola parabola-2015.05.01-dual.iso

Steps to reproduce:

#mkfs.btrfs -f /dev/sda
#mount -o compress=lzo /dev/sda /mnt
#pacstrap /mnt base

Error output:

<snip>

  which-2.21-1-x86_64       14.7 KiB  0.00B/s 00:00  
[##########################] 100%
  xfsprogs-3.2.2-1-x86_64  689.6 KiB   438K/s 00:02  
[##########################] 100%
(127/127) checking keys in keyring                  
[##########################] 100%
(127/127) checking package integrity                
[##########################] 100%
error: filesystem: signature from "André Silva <emulatorman at riseup.net>"  
is unknown trust
:: File  
/mnt/var/cache/pacman/pkg/filesystem-2015.02-1.parabola1-x86_64.pkg.tar.xz  
is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: licenses: signature from "André Silva <emulatorman at riseup.net>" is  
unknown trust
:: File  
/mnt/var/cache/pacman/pkg/licenses-20140629-1.parabola1-any.pkg.tar.xz is  
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: linux-libre-api-headers: signature from "André Silva  
<emulatorman at riseup.net>" is unknown trust
:: File  
/mnt/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]
error: ath9k-htc-firmware: signature from "André Silva  
<emulatorman at riseup.net>" is unknown trust
:: File  
/mnt/var/cache/pacman/pkg/ath9k-htc-firmware-1.4.0-1-any.pkg.tar.xz is  
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: openfwwf: signature from "André Silva <emulatorman at riseup.net>" is  
unknown trust
:: File /mnt/var/cache/pacman/pkg/openfwwf-5.2-2-any.pkg.tar.xz is  
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: linux-libre-firmware: signature from "André Silva  
<emulatorman at riseup.net>" is unknown trust
:: File  
/mnt/var/cache/pacman/pkg/linux-libre-firmware-4.0_gnu-1-any.pkg.tar.xz is  
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: linux-libre: signature from "André Silva <emulatorman at riseup.net>"  
is unknown trust
:: File  
/mnt/var/cache/pacman/pkg/linux-libre-4.0.6_gnu-1-x86_64.pkg.tar.xz is  
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: pacman-mirrorlist: signature from "André Silva  
<emulatorman at riseup.net>" is unknown trust
:: File  
/mnt/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]
error: parabola-keyring: signature from "André Silva  
<emulatorman at riseup.net>" is unknown trust
:: File  
/mnt/var/cache/pacman/pkg/parabola-keyring-20150624-1-any.pkg.tar.xz is  
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: pacman: signature from "André Silva <emulatorman at riseup.net>" is  
unknown trust
:: File  
/mnt/var/cache/pacman/pkg/pacman-4.2.1-1.parabola1-x86_64.pkg.tar.xz is  
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: your-freedom: signature from "André Silva  
<emulatorman at riseup.net>" is unknown trust
:: File /mnt/var/cache/pacman/pkg/your-freedom-20150622-1-any.pkg.tar.xz  
is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: failed to commit transaction (invalid or corrupted package)
Errors occurred, no packages were upgraded.
==> ERROR: Failed to install packages to new root
pacstrap /mnt base  6.74s user 10.47s system 6% cpu 4:06.64 total