Filed by: apavel [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer.html#?job_id=275507196&repo=mozilla-central
Full log: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/IhJ5bpIzSjiAs4x0bgyChA/runs/0/artifacts/public/logs/live_backing.log

[task 2019-11-10T00:04:22.129Z] 00:04:22 INFO - TEST-START | awsy/test_memory_usage.py TestMemoryUsage.test_open_tabs
[task 2019-11-10T00:04:22.134Z] 00:04:22 INFO - areweslimyet run by 100 pages, 3 iterations, 10 perTabPause, 30 settleWaitTime
[task 2019-11-10T00:04:22.139Z] 00:04:22 INFO - setting up
[task 2019-11-10T00:04:22.342Z] 00:04:22 INFO - port {} error {}
[task 2019-11-10T00:04:22.359Z] 00:04:22 INFO - TEST-UNEXPECTED-ERROR | awsy/test_memory_usage.py TestMemoryUsage.test_open_tabs | AttributeError: 'NoneType' object has no attribute 'format'
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - Traceback (most recent call last):
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - File "/Users/cltbld/tasks/task_1573344167/build/venv/lib/python2.7/site-packages/marionette_harness/marionette_test/testcases.py", line 140, in run
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - self.setUp()
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - File "/Users/cltbld/tasks/task_1573344167/build/tests/awsy/awsy/test_memory_usage.py", line 138, in setUp
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - self.setupTp5()
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - File "/Users/cltbld/tasks/task_1573344167/build/tests/awsy/awsy/test_memory_usage.py", line 66, in setupTp5
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - self._webservers.start()
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - File "/Users/cltbld/tasks/task_1573344167/build/venv/lib/python2.7/site-packages/awsy/webservers.py", line 47, in start
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - print("port {} error {}").format(port, error)
[task 2019-11-10T00:04:22.360Z] 00:04:22 INFO - TEST-INFO took 216ms
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO -
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - SUMMARY
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - -------
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - passed: 0
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - failed: 1
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - todo: 0
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO -
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - FAILED TESTS
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - -------
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - test_memory_usage.py test_memory_usage.TestMemoryUsage.test_open_tabs
[task 2019-11-10T00:04:54.259Z] 00:04:54 INFO - SUITE-END | took 32s
[task 2019-11-10T00:04:54.779Z] 00:04:54 ERROR - Return code: 10
[task 2019-11-10T00:04:54.780Z] 00:04:54 ERROR - Got 1 unexpected statuses
[task 2019-11-10T00:04:54.780Z] 00:04:54 INFO - AWSY exited with return code 10: WARNING
[task 2019-11-10T00:04:54.780Z] 00:04:54 WARNING - # TBPL WARNING #
[task 2019-11-10T00:04:54.780Z] 00:04:54 WARNING - setting return code to 1

Seems to be fixed by commit https://hg.mozilla.org/mozilla-central/rev/7a75cab3dd550b77ba4f748b31c1b45ce2784c84

https://treeherder.mozilla.org/#/jobs?repo=mozilla-central&group_state=expanded&selectedJob=275507196&resultStatus=success%2Ctestfailed%2Cbusted%2Cexception&searchStr=os%2Cx%2C10.14%2Cshippable%2Copt%2Care%2Cwe%2Cslim%2Cyet%2Ctests%2Cby%2Ctaskcluster%2Ctest-macosx1014-64-shippable%2Fopt-awsy-e10s%2Csy%28sy%29