Some Provision jobs are failing with a distinct signature.
I've seen it on the CQ; presumably it can happen anywhere.

Here are links to a handful of recent provision job failures
showing the signature:
    http://cautotest.corp.google.com/tko/retrieve_logs.cgi?job=/results/102074215-chromeos-test/chromeos4-row9-rack7-host15/
    http://cautotest.corp.google.com/tko/retrieve_logs.cgi?job=/results/102074351-chromeos-test/chromeos4-row9-rack9-host20/
    http://cautotest.corp.google.com/tko/retrieve_logs.cgi?job=/results/102074536-chromeos-test/chromeos4-row1-rack12-host7/

The key part of the signature is this exception traceback
in the status.log file:
  Traceback (most recent call last):
    File "/usr/local/autotest/client/common_lib/test.py", line 804, in _call_test_function
      return func(*args, **dargs)
    File "/usr/local/autotest/client/common_lib/test.py", line 461, in execute
      dargs)
    File "/usr/local/autotest/client/common_lib/test.py", line 347, in _call_run_once_with_retry
      postprocess_profiled_run, args, dargs)
    File "/usr/local/autotest/client/common_lib/test.py", line 376, in _call_run_once
      self.run_once(*args, **dargs)
    File "/usr/local/autotest/server/site_tests/provision_AutoUpdate/provision_AutoUpdate.py", line 113, in run_once
      force_full_update=force)
    File "/usr/local/autotest/server/afe_utils.py", line 232, in machine_install_and_update_labels
      *args, **dargs)
    File "/usr/local/autotest/server/hosts/cros_host.py", line 728, in machine_install_by_devserver
      full_update=force_full_update)
    File "/usr/local/autotest/client/common_lib/cros/dev_server.py", line 2013, in auto_update
      raise DevServerException(error_msg % (host_name, error_list[0]))
  DevServerException: CrOS auto-update failed for host chromeos4-row1-rack12-host7: No JSON object could be decoded

I haven't figured out where exactly the exception is coming from.