This looks like it was caused by https://hg.mozilla.org/mozilla-central/rev/cb5bc98d8aab12a622f2df4c697d1e7ea9a73418. Luca, could you please take a look?
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This looks like it was caused by https://hg.mozilla.org/mozilla-central/rev/cb5bc98d8aab12a622f2df4c697d1e7ea9a73418. So far it only fails on tests with fission enabled: https://treeherder.mozilla.org/#/jobs?repo=mozilla-central&group_state=expanded&resultStatus=testfailed%2Cbusted%2Cexception&revision=dc056be018fe8400010ef3169ff13ff739758a33&test_paths=devtools%2Fclient%2Finspector%2Ftest%2F&selectedTaskRun=EhettgH0RVu5jwr2i0Q7bQ.0 Luca, could you please take a look?