This has been around for a long time. Not only Chromeboxes

https://stainless.corp.google.com/search?view=list&first_date=2018-05-17&last_date=2018-09-13&test=%5Egraphics%5C_VideoRenderingPower%5C.vp9%24&reason=Unhandled+AttributeError%3A+%27NoneType%27+object+has+no+attribute+%27endswith%27&exclude_cts=true&exclude_not_run=false&exclude_non_release=true&exclude_au=true&exclude_acts=true&exclude_retried=true&exclude_non_production=false

09/09 19:17:29.296 WARNI|              test:0606| The test failed with the following exception
Traceback (most recent call last):
  File "/usr/local/autotest/common_lib/test.py", line 600, in _exec
    _call_test_function(self.execute, *p_args, **p_dargs)
  File "/usr/local/autotest/common_lib/test.py", line 806, in _call_test_function
    raise error.UnhandledTestFail(e)
UnhandledTestFail: Unhandled AttributeError: 'NoneType' object has no attribute 'endswith'
Traceback (most recent call last):
  File "/usr/local/autotest/common_lib/test.py", line 800, in _call_test_function
    return func(*args, **dargs)
  File "/usr/local/autotest/common_lib/test.py", line 464, in execute
    postprocess_profiled_run, args, dargs)
  File "/usr/local/autotest/common_lib/test.py", line 371, in _call_run_once
    self.run_once(*args, **dargs)
  File "/usr/local/autotest/tests/graphics_VideoRenderingPower/graphics_VideoRenderingPower.py", line 79, in run_once
    rapl = [power_status.SystemPower(self._power_status.battery_path)]
  File "/usr/local/autotest/cros/power/power_status.py", line 1395, in __init__
    self._voltage_file = os.path.join(battery_dir, 'voltage_now')
  File "/usr/local/lib64/python2.7/posixpath.py", line 70, in join
    elif path == '' or path.endswith('/'):
AttributeError: 'NoneType' object has no attribute 'endswith'