I am guessing (from the code paths) that this is happening on the devserver?

https://uberchromegw.corp.google.com/i/chromeos/builders/caroline-release/builds/231/steps/Paygen/logs/stdio

06:39:58: INFO: RunCommand: /b/cbuild/internal_master/.cache/common/gsutil_4.19.tar.gz/gsutil/gsutil cp /tmp/cbuildbot-tmpIGUxuk/tmpBbP7VE/paygen_payload.cGDKIM/delta.json gs://chromeos-releases/dev-channel/caroline/9108.0.0/payloads/chromeos_9000.26.0-9108.0.0_caroline_dev-channel_delta_test.bin-4bb7ddb35c1542c1ff08b414b2306e75.json
06:39:59: INFO: * Finished payload generation in 0:32:07.937267
06:40:27: INFO: RunCommand: /b/cbuild/internal_master/.cache/common/gsutil_4.19.tar.gz/gsutil/gsutil -o 'Boto:num_retries=10' -h x-goog-if-generation-match:1482329266882755 rm gs://chromeos-releases/dev-channel/caroline/9108.0.0/payloads/LOCK_flag
06:40:28: ERROR: Failed: Build definition (board='caroline', version='9108.0.0', channel='dev-channel')

@@@STEP_FAILURE@@@
06:40:28: ERROR: <type 'exceptions.IOError'>: [Errno 28] No space left on device
Traceback (most recent call last):
  File "/b/cbuild/internal_master/chromite/lib/parallel.py", line 602, in TaskRunner
    task(*x, **task_kwargs)
  File "/b/cbuild/internal_master/chromite/lib/parallel.py", line 800, in <lambda>
    fn = lambda idx, task_args: out_queue.put((idx, task(*task_args)))
  File "/b/cbuild/internal_master/chromite/lib/paygen/paygen_build_lib.py", line 268, in _GenerateSinglePayload
    dry_run=dry_run)
  File "/b/cbuild/internal_master/chromite/lib/paygen/paygen_payload_lib.py", line 837, in CreateAndUploadPayload
    dry_run=dry_run).Run()
  File "/b/cbuild/internal_master/chromite/lib/paygen/paygen_payload_lib.py", line 707, in Run
    self._drm(self._VerifyPayload)
  File "/b/cbuild/internal_master/chromite/lib/paygen/dryrun_lib.py", line 45, in __call__
    return self.Run(func, *args, **kwargs)
  File "/b/cbuild/internal_master/chromite/lib/paygen/dryrun_lib.py", line 82, in Run
    return self._Call(func, *args, **kwargs)
  File "/b/cbuild/internal_master/chromite/lib/paygen/dryrun_lib.py", line 86, in _Call
    return func(*args, **kwargs)
  File "/b/cbuild/internal_master/chromite/lib/paygen/paygen_payload_lib.py", line 681, in _VerifyPayload
    self._ApplyPayload(payload, is_delta)
  File "/b/cbuild/internal_master/chromite/lib/paygen/paygen_payload_lib.py", line 641, in _ApplyPayload
    payload.Apply(bspatch_path=bspatch_path, **part_files)
  File "/b/cbuild/internal_master/src/platform/dev/host/lib/update_payload/payload.py", line 321, in Apply
    old_rootfs_part=old_rootfs_part)
  File "/b/cbuild/internal_master/src/platform/dev/host/lib/update_payload/applier.py", line 569, in Run
    self.payload.manifest.old_rootfs_info)
  File "/b/cbuild/internal_master/src/platform/dev/host/lib/update_payload/applier.py", line 517, in _ApplyToPartition
    new_part_file, new_part_info.size)
  File "/b/cbuild/internal_master/src/platform/dev/host/lib/update_payload/applier.py", line 458, in _ApplyOperations
    self._ApplyReplaceOperation(op, op_name, data, new_part_file, part_size)
  File "/b/cbuild/internal_master/src/platform/dev/host/lib/update_payload/applier.py", line 269, in _ApplyReplaceOperation
    part_file.write(out_data[data_start:data_end])
IOError: [Errno 28] No space left on device

<type 'exceptions.IOError'>: [Errno 28] No space left on device