Oh wow, I haven't thought that we still run some Fennec specific scripts for Marionette in mozharness. So in the `android_emulator_pgo.py` file the `Marionette.quit()` isn't used but some custom script evaluation which indeed fails. It should really use Marionette's `in_app` shutdown logic here. https://searchfox.org/mozilla-central/rev/64f196824745c5db5ef7bb23725cfb9a41586149/testing/mozharness/scripts/android_emulator_pgo.py#248-261
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Oh wow, I haven't thought that we still run some Fennec specific scripts for Marionette in mozharness. So in the `android_emulator_pgo.py` file the `Marionette.quit()` isn't used but some custom script evaluation which indeed fails. It should really use Marionette's `in_app` shutdown logic here. https://searchfox.org/mozilla-central/rev/64f196824745c5db5ef7bb23725cfb9a41586149/testing/mozharness/scripts/android_emulator_pgo.py#248-261 Here a try build for the patch fixing this issue: https://treeherder.mozilla.org/jobs?repo=try&revision=26b8e42c9135eec39e01a0c0d7cb50ff4c8fb29d