Seen in https://integration.wikimedia.org/ci/job/wmf-quibble-selenium-php72-docker/21548/console on mw core patch to wmf deployment branch
(https://gerrit.wikimedia.org/r/#/c/mediawiki/core/+/573993/)
Also in https://gerrit.wikimedia.org/r/572265 on https://integration.wikimedia.org/ci/job/wmf-quibble-selenium-php72-docker/21547/console
```
14:28:50 [0-1] 2020-02-21T13:28:50.016Z ERROR webdriver: Request failed due to Error: unknown command: session/dbb8ec040c577d8f66a670f4257bb328/se/log
14:28:50 at getErrorFromResponseBody (/workspace/src/extensions/Wikibase/client/data-bridge/node_modules/webdriver/build/utils.js:117:12)
14:28:50 at Request._callback (/workspace/src/extensions/Wikibase/client/data-bridge/node_modules/webdriver/build/request.js:111:64)
14:28:50 at Request.self.callback (/workspace/src/extensions/Wikibase/client/data-bridge/node_modules/request/request.js:185:22)
14:28:50 at Request.emit (events.js:189:13)
14:28:50 at Request.EventEmitter.emit (domain.js:441:20)
14:28:50 at Request.<anonymous> (/workspace/src/extensions/Wikibase/client/data-bridge/node_modules/request/request.js:1154:10)
14:28:50 at Request.emit (events.js:189:13)
14:28:50 at Request.EventEmitter.emit (domain.js:441:20)
14:28:50 at IncomingMessage.<anonymous> (/workspace/src/extensions/Wikibase/client/data-bridge/node_modules/request/request.js:1076:12)
14:28:50 at Object.onceWrapper (events.js:277:13)
14:28:50 at IncomingMessage.emit (events.js:194:15)
14:28:50 at IncomingMessage.EventEmitter.emit (domain.js:441:20)
14:28:50 at endReadableNT (_stream_readable.js:1103:12)
14:28:50 at process._tickCallback (internal/process/next_tick.js:63:19)
14:28:50 2020-02-21T13:28:50.018Z ERROR @wdio/sync: Error: unknown command: session/dbb8ec040c577d8f66a670f4257bb328/se/log
14:28:50 at endReadableNT (_stream_readable.js:1103:12)
14:28:50 at Object.afterTest (/workspace/src/extensions/Wikibase/client/data-bridge/tests/selenium/wdio.conf.js:158:14)
14:28:50 [0-1] Error in "AfterTest Hook"
14:28:50 unknown command: session/dbb8ec040c577d8f66a670f4257bb328/se/log
14:28:50 [0-1] Error in "App closes on clicking the cancel button"
```