We have seen three consecutive errors that look like an actual failure
in the range 2017-05-05 01:00-15:31 UTC. The errors afterwards were
caused by issue 719233, and we can safely ignore them.

The three failures contain a python error like this in the end of
the test:

> Traceback (most recent call last):
>   File "/b/swarm_slave/w/ir/build/android/test_runner.py", line 917, in main
>     return RunTestsCommand(args)
>   File "/b/swarm_slave/w/ir/build/android/test_runner.py", line 676, in RunTestsCommand
>     return RunTestsInPlatformMode(args)
>   File "/b/swarm_slave/w/ir/build/android/test_runner.py", line 836, in RunTestsInPlatformMode
>     str(iteration_count))
>   File "/b/swarm_slave/w/ir/third_party/catapult/common/py_utils/py_utils/contextlib_ext.py", line 19, in __exit__
>     return self._manager.__exit__(exc_type, exc_val, exc_tb)
>   File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
>     self.gen.next()
>   File "/b/swarm_slave/w/ir/build/android/test_runner.py", line 744, in write_json_file
>     all_raw_results, args.json_results_file)
>   File "/b/swarm_slave/w/ir/build/android/pylib/results/json_results.py", line 138, in GenerateJsonResultsFile
>     json_result_file.write(json.dumps(GenerateResultsDict(test_run_result)))
>   File "/usr/lib/python2.7/json/__init__.py", line 243, in dumps
>     return _default_encoder.encode(obj)
>   File "/usr/lib/python2.7/json/encoder.py", line 207, in encode
>     chunks = self.iterencode(o, _one_shot=True)
>   File "/usr/lib/python2.7/json/encoder.py", line 270, in iterencode
>     return _iterencode(o, 0)
> UnicodeDecodeError: 'utf8' codec can't decode byte 0xd8 in position 153: invalid continuation byte

It's 2017-05-08 05:45 UTC now, which means we haven't seen the similar
failures for the last three days (though these days are mostly weekends).
So the error may be already fixed; let's watch the trybot status
for a few days to see if the similar failure occurs again.

There has been no errors for these two days. I assume this was fixed elsewhere.