A CL that passes in tryjobs run on the old scheduler fails auto-updating when scheduled with Swarming. (Specifically, the test is crostestutils.au_test_harness.au_test.AUTest SimpleTestUpdateAndVerify, failure log here: gpaste/6161522594152448)

Here are five swarming tryjob runs of the same patch, all of which fail in the same place:
cros-goldeneye/chromeos/healthmonitoring/buildDetails?buildbucketId=8953313552598843296
cros-goldeneye/chromeos/healthmonitoring/buildDetails?buildbucketId=8953313557239412992
cros-goldeneye/chromeos/healthmonitoring/buildDetails?buildbucketId=8953313562301043456
cros-goldeneye/chromeos/healthmonitoring/buildDetails?buildbucketId=8953313568290739952
cros-goldeneye/chromeos/healthmonitoring/buildDetails?buildbucketId=8953313574574810592

Another, same patch, run with the old scheduler, which succeeds:
cros-goldeneye/chromeos/healthmonitoring/buildDetails?buildbucketId=8953313542669609424

And a run of ToT which fails in that place:
cros-goldeneye/chromeos/healthmonitoring/buildDetails?buildbucketId=8953306813041576976