test_invalid_utf8 test failing on some buildbots

[mdboom]

The test added in #94856 is failing on a number of buildbots:

• https://buildbot.python.org/all/#/builders/188
• https://buildbot.python.org/all/#/builders/285
• https://buildbot.python.org/all/#/builders/33
• https://buildbot.python.org/all/#/builders/455
• https://buildbot.python.org/all/#/builders/40
• https://buildbot.python.org/all/#/builders/339

[hauntsaninja]

Thanks for fixing, looks like this has been completed