https://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29

telemetry_unittests on Windows-7-SP1 seems to be failing occasionally with an error related to decoding ascii. Here's the stack trace:

[1032/1056] telemetry.core.tracing_controller_unittest.TracingControllerTest.testStartupTracingOnDesktop queued(INFO) 2016-11-29 12:03:59,687 pid=5132  exception_formatter.PrintFormattedException:19  Try printing formatted exception: <type 'exceptions.UnicodeDecodeError'> 'ascii' codec can't decode byte 0x81 in position 8045: ordinal not in range(128) <traceback object at 0x04B09558>

Traceback (most recent call last):
  <module> at e:\b\swarm_slave\w\irej0dag\third_party\catapult\telemetry\telemetry\testing\run_tests.py:298
    ret_code = RunTestsCommand.main()
  main at e:\b\swarm_slave\w\irej0dag\third_party\catapult\telemetry\telemetry\testing\run_tests.py:119
    return obj.Run(options)
  Run at e:\b\swarm_slave\w\irej0dag\third_party\catapult\telemetry\telemetry\testing\run_tests.py:191
    ret, _, _ = runner.run()
  run at e:\b\swarm_slave\w\irej0dag\third_party\catapult\third_party\typ\typ\runner.py:178
    ret, full_results = self._run_tests(result_set, test_set)
  _run_tests at e:\b\swarm_slave\w\irej0dag\third_party\catapult\third_party\typ\typ\runner.py:426
    self._run_one_set(self.stats, result_set, test_set)
  _run_one_set at e:\b\swarm_slave\w\irej0dag\third_party\catapult\third_party\typ\typ\runner.py:471
    test_set.isolated_tests, 1)
  _run_list at e:\b\swarm_slave\w\irej0dag\third_party\catapult\third_party\typ\typ\runner.py:507
    result = pool.get()
  get at e:\b\swarm_slave\w\irej0dag\third_party\catapult\third_party\typ\typ\pool.py:195
    return self.callback(self.context_after_pre, self.msgs.pop(0))
  _run_one_test at e:\b\swarm_slave\w\irej0dag\third_party\catapult\third_party\typ\typ\runner.py:854
    err, child.worker_num, pid)
  _result_from_test_result at e:\b\swarm_slave\w\irej0dag\third_party\catapult\third_party\typ\typ\runner.py:882
    err = err + test_result.errors[0][1]
UnicodeDecodeError: 'ascii' codec can't decode byte 0x81 in position 8045: ordinal not in range(128)

Here are two example runs where this happened:

https://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/55152/steps/telemetry_unittests%20on%20Windows-7-SP1/logs/stdio

https://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/55152/steps/telemetry_unittests%20on%20Windows-7-SP1/logs/stdio

Looking at the builder, it seems like we tend to get a streak of Telemetry failures per day, and the rest of the runs are successful.

nednguyen@, any idea what might be going on?