Filed by: rmaries [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer.html#?job_id=317383652&repo=autoland
Full log: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/V0ojjN0xT2-AbVk4uQl2lA/runs/0/artifacts/public/logs/live_backing.log

[task 2020-10-02T11:28:35.969Z] 11:28:35     INFO - TEST-START | /webdriver/tests/perform_actions/key.py
[task 2020-10-02T11:28:40.543Z] 11:28:40     INFO - STDOUT: ___________________________ test_no_browsing_context ___________________________
[task 2020-10-02T11:28:40.544Z] 11:28:40     INFO - STDOUT: session = <Session f1a057a5-d84f-4100-b2f9-8be8b07570c3>, closed_frame = None
[task 2020-10-02T11:28:40.545Z] 11:28:40     INFO - STDOUT: key_chain = <webdriver.client.ActionSequence object at 0x7fb6d22d5b10>
[task 2020-10-02T11:28:40.545Z] 11:28:40     INFO - STDOUT:     def test_no_browsing_context(session, closed_frame, key_chain):
[task 2020-10-02T11:28:40.546Z] 11:28:40     INFO - STDOUT:         with pytest.raises(NoSuchWindowException):
[task 2020-10-02T11:28:40.547Z] 11:28:40     INFO - STDOUT: >           key_chain.key_up("a").perform()
[task 2020-10-02T11:28:40.550Z] 11:28:40     INFO - STDOUT: E           Failed: DID NOT RAISE <class 'webdriver.error.NoSuchWindowException'>
[task 2020-10-02T11:28:40.550Z] 11:28:40     INFO - STDOUT: closed_frame = None
[task 2020-10-02T11:28:40.553Z] 11:28:40     INFO - STDOUT: key_chain  = <webdriver.client.ActionSequence object at 0x7fb6d22d5b10>
[task 2020-10-02T11:28:40.553Z] 11:28:40     INFO - STDOUT: session    = <Session f1a057a5-d84f-4100-b2f9-8be8b07570c3>
[task 2020-10-02T11:28:40.553Z] 11:28:40     INFO - STDOUT: tests/web-platform/tests/webdriver/tests/perform_actions/key.py
[task 2020-10-02T11:28:40.553Z] 11:28:40     INFO - STDOUT: :21: Failed
[task 2020-10-02T11:28:40.553Z] 11:28:40     INFO - STDOUT: ====================== 1 failed, 4 passed in 4.32 seconds ======================
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - 
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - TEST-PASS | /webdriver/tests/perform_actions/key.py | test_null_response_value 
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - TEST-PASS | /webdriver/tests/perform_actions/key.py | test_no_top_browsing_context 
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - TEST-UNEXPECTED-FAIL | /webdriver/tests/perform_actions/key.py | test_no_browsing_context - Failed: DID NOT RAISE <class 'webdriver.error.NoSuchWindowException'>
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - session = <Session f1a057a5-d84f-4100-b2f9-8be8b07570c3>, closed_frame = None
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - key_chain = <webdriver.client.ActionSequence object at 0x7fb6d22d5b10>
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - 
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO -     def test_no_browsing_context(session, closed_frame, key_chain):
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO -         with pytest.raises(NoSuchWindowException):
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - >           key_chain.key_up("a").perform()
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - E           Failed: DID NOT RAISE <class 'webdriver.error.NoSuchWindowException'>
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - 
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - closed_frame = None
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - key_chain  = <webdriver.client.ActionSequence object at 0x7fb6d22d5b10>
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - session    = <Session f1a057a5-d84f-4100-b2f9-8be8b07570c3>
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - 
[task 2020-10-02T11:28:40.555Z] 11:28:40     INFO - tests/web-platform/tests/webdriver/tests/perform_actions/key.py:21: Failed```

Should be identical to bug 1665250 but the action chains raise a specific error here.

As it looks like this failure has been fixed with my patch on bug 1666204. Feel free to reopen in the case that it happens again over the next days.