Web platform tests have HSTS priming disabled because the HSTS priming HEAD request triggers a UnicodeDecodeError in BaseHttpServer.py at https://github.com/python/cpython/blob/2.7/Lib/BaseHTTPServer.py#L279. Currently investigating whether the issue is the web-platform test framework, python, or Necko, and will file bugs as appropriate.
Created attachment 8855521 [details] [diff] [review] Test-only patch to re-enable HSTS priming on web-platform tests Re-enable hsts priming for web platform tests. try: https://treeherder.mozilla.org/#/jobs?repo=try&revision=ce2b4a8cbd0654a748f2f21c52c65f1002718281
Try run has no web platform test failures, marking checkin needed.
Pushed by email@example.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/256f7bc3bf9a Re-enable HSTS priming on web-platform tests. r=test-only