Just an FYI that this change is generating warnings on my Windows 10 buildbot with some regularity about a failure to parse testperf output, such as:

Warning -- Failed to parse typeperf output: '"10/01/2019 07:58:50.056"'

from https://buildbot.python.org/all/#/builders/217/builds/487

Now, clearly there's no queue length in that output so the parsing warning is accurate, but does the overall build have to reflect a warning in such cases, given that it's just a test harness issue, and not anything going wrong with the actual tests?  Previously any such cases would be ignored silently, so this probably isn't a new issue but just one that is now shows up as an overall build warning.

I don't know why both fields aren't present although it seems plausible that it's just a partial line from the I/O (I don't think it guarantees it receives full lines), and the queue length field would appear on the following read.