I'm following the instructions here to build ChromeOS for the first time: http://www.chromium.org/chromium-os/developer-guide

It's failing on the "./build_packages --board=veyron" step.

ChromeOS version information:
    CHROME_BRANCH=54
    CHROME_VERSION=
    CHROMEOS_VERSION_STRING=8599.0.2016_07_17_2108
    CHROME_BASE=

=== Start output for job deqp-2016.06.20-r1 (0m1.0s) ===
deqp-2016.06.20-r1: >>> Emerging (1 of 1) media-gfx/deqp-2016.06.20-r1::chromiumos for /build/veyron/
deqp-2016.06.20-r1:   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
deqp-2016.06.20-r1:                                  Dload  Upload   Total   Spent    Left  Speed
deqp-2016.06.20-r1: 
deqp-2016.06.20-r1:   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
deqp-2016.06.20-r1:   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
deqp-2016.06.20-r1:   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
deqp-2016.06.20-r1: curl: (22) The requested URL returned error: 403 Forbidden
deqp-2016.06.20-r1:   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
deqp-2016.06.20-r1:                                  Dload  Upload   Total   Spent    Left  Speed
deqp-2016.06.20-r1: 
deqp-2016.06.20-r1:   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
deqp-2016.06.20-r1:   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
deqp-2016.06.20-r1: curl: (22) The requested URL returned error: 404 Not Found
deqp-2016.06.20-r1: !!! Couldn't download 'deqp-4e0555590ea2e0c08b7333773543f03fc5e12d21.tar.gz'. Aborting.
deqp-2016.06.20-r1:  * Fetch failed for 'media-gfx/deqp-2016.06.20-r1', Log file:
deqp-2016.06.20-r1:  *  '/build/veyron/tmp/portage/logs/media-gfx:deqp-2016.06.20-r1:20160717-203019.log'
deqp-2016.06.20-r1: >>> Failed to emerge media-gfx/deqp-2016.06.20-r1 for /build/veyron/, Log file:
deqp-2016.06.20-r1: >>>  '/build/veyron/tmp/portage/logs/media-gfx:deqp-2016.06.20-r1:20160717-203019.log'
deqp-2016.06.20-r1: 
deqp-2016.06.20-r1:  * Messages for package media-gfx/deqp-2016.06.20-r1 merged to /build/veyron/:
deqp-2016.06.20-r1: 
deqp-2016.06.20-r1:  * Fetch failed for 'media-gfx/deqp-2016.06.20-r1', Log file:
deqp-2016.06.20-r1:  *  '/build/veyron/tmp/portage/logs/media-gfx:deqp-2016.06.20-r1:20160717-203019.log'
=== Complete: job deqp-2016.06.20-r1 (0m1.0s) ===
Failed media-gfx/deqp-2016.06.20-r1 (in 0m1.0s). Your build has failed.
Pending 9/618, [Time 20:30:20 | Elapsed 191m22.6s | Load 1.23 3.74 6.39]
Packages failed:
        chromeos-base/dev-install-0.0.1-r839
        media-gfx/deqp-2016.06.20-r1