https://cros-goldeneye.corp.google.com/chromeos/legoland/builderHistory?buildConfig=sarien-release&buildBranch=master

The sarien-release builder has been failing for several days with an error at the end of build packages, yet it seems the build itself succeeds.

https://luci-logdog.appspot.com/logs/chromeos/buildbucket/cr-buildbucket.appspot.com/8924876719401983504/+/steps/BuildPackages__afdo_use_/0/stdout

----------
Completed chromeos-base/autotest-all-0.0.1-r48 (in 0m9.3s)
Pending 0/879, [Time 13:01:51 | Elapsed 121m18.0s | Load 2.81 4.26 6.5]
Merge complete
Done
using /tmp/goma_tmp_dir.zStSCX as tmpdir
Killing compiler proxy.
compiler proxy status: http://127.0.0.1:8088 quit!
Builds complete
INFO    : fetching the debug symbols
13:01:53: INFO: nothing to do, exit
INFO    : Elapsed time (build_packages): 122m26s
Done
13:01:54: INFO: Archive build-events.json file

13:01:54: ERROR: <type 'exceptions.ValueError'>: Expecting , delimiter: line 3 column 1 (char 55)
Traceback (most recent call last):
  File "/b/swarming/wHmoldo/ir/cache/cbuild/repository/chromite/lib/failures_lib.py", line 230, in wrapped_functor
    return functor(*args, **kwargs)
  File "/b/swarming/wHmoldo/ir/cache/cbuild/repository/chromite/cbuildbot/stages/generic_stages.py", line 1171, in UploadArtifact
    upload_urls = self._GetUploadUrls(filename)
  File "/b/swarming/wHmoldo/ir/cache/cbuild/repository/chromite/cbuildbot/stages/generic_stages.py", line 1148, in _GetUploadUrls
    json_file = json.loads(custom_artifacts_file)
  File "/usr/lib/python2.7/json/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python2.7/json/decoder.py", line 382, in raw_decode
    obj, end = self.scan_once(s, idx)
ValueError: Expecting , delimiter: line 3 column 1 (char 55)
----------

I don't see any other builder failing like this, and the diff between the last passing and failing build is at:\
https://crosland.corp.google.com/log/11521.0.0..11522.0.0

The only sarien-specific change is https://chrome-internal.googlesource.com/chromeos/overlays/overlay-sarien-private/+/89d8344fc7c7621fbe8d3d78668f894164c54bf6

It looks like the json format is not correct in that change, the 'extra_upload_urls' should be an array with multiple entries, not declared twice.

BAD:
{
  "extra_upload_urls": ["gs://chromeos-moblab-one"]
  "extra_upload_urls": ["gs://chromeos-moblab-two"]
}

GOOD:
{
  "extra_upload_urls": ["gs://chromeos-moblab-one",
                        "gs://chromeos-moblab-two"]
}