test: fix weird string error

[maclover7]

Previously getting this error when running tap2junit (what parses our
.tap files in CI):

Traceback (most recent call last):
  File "/usr/local/bin/tap2junit", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python2.7/site-packages/tap2junit/__main__.py", line 46, in main
    result.to_file(args.output, [result], prettyprint=False)
  File "/usr/local/lib/python2.7/site-packages/junit_xml/__init__.py", line 289, in to_file
    test_suites, prettyprint=prettyprint, encoding=encoding)
  File "/usr/local/lib/python2.7/site-packages/junit_xml/__init__.py", line 257, in to_xml_string
    ts_xml = ts.build_xml_doc(encoding=encoding)
  File "/usr/local/lib/python2.7/site-packages/junit_xml/__init__.py", line 221, in build_xml_doc
    attrs['message'] = decode(case.skipped_message, encoding)
  File "/usr/local/lib/python2.7/site-packages/junit_xml/__init__.py", line 68, in decode
    ret = unicode(var)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 11: ordinal not in range(128)

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[nodejs-github-bot]

@maclover7 build started: https://ci.nodejs.org/blue/organizations/jenkins/node-test-pull-request-lite-pipeline/detail/node-test-pull-request-lite-pipeline/263/pipeline

[maclover7]

This, with #21791, will make --worker tests pass in CI :)

[addaleax]

LGTM as a workaround, but please let’s also fix this upstream :/

[maclover7]

Full CI: https://ci.nodejs.org/job/node-test-pull-request/15852/

Edit by @addaleax: CI came back green, please 👍 to approve fast-tracking

[addaleax]

Landed in 2d95070, thanks!