Filed by: nbeleuzu [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer.html#?job_id=254005186&repo=autoland
Full log: https://queue.taskcluster.net/v1/task/FA_NtvnoRdSSIlh5qQLxZw/runs/0/artifacts/public/logs/live_backing.log

[task 2019-06-28T22:02:35.733Z] 22:02:35 INFO - MOZ_NODE_PATH environment variable not set. Tests requiring http/2 will fail.
[task 2019-06-28T22:02:35.956Z] 22:02:35 INFO - Running tests sequentially.
[task 2019-06-28T22:02:35.958Z] 22:02:35 INFO - SUITE-START | Running 1350 tests
[task 2019-06-28T22:02:36.575Z] 22:02:36 INFO - TEST-START | netwerk/test/unit/test_bug1378385_http1.js
[task 2019-06-28T22:02:36.981Z] 22:02:36 WARNING - TEST-UNEXPECTED-FAIL | netwerk/test/unit/test_bug1378385_http1.js | xpcshell return code: 0
[task 2019-06-28T22:02:36.981Z] 22:02:36 INFO - TEST-INFO took 407ms
[task 2019-06-28T22:02:36.981Z] 22:02:36 INFO - >>>>>>>
[task 2019-06-28T22:02:36.982Z] 22:02:36 INFO - netwerk/test/unit/test_bug1378385_http1.js | /data/local/xpcb/xpcw[17]: cd: /sdcard/tests/xpc/netwerk/test/unit: No such file or directory
[task 2019-06-28T22:02:36.982Z] 22:02:36 INFO - netwerk/test/unit/test_bug1378385_http1.js | xpcw: cd /sdcard/tests/xpc/netwerk/test/unit
[task 2019-06-28T22:02:36.982Z] 22:02:36 INFO - netwerk/test/unit/test_bug1378385_http1.js | xpcw: xpcshell -r /sdcard/tests/xpc/c/httpd.manifest --greomni /data/local/xpcb/target.apk -m -s -e const _HEAD_JS_PATH = "/sdcard/tests/xpc/head.js"; -e const _MOZINFO_JS_PATH = "/sdcard/tests/xpc/p/mozinfo.json"; -e const _PREFS_FILE = "/sdcard/tests/xpc/user.js"; -e const _TESTING_MODULES_DIR = "/sdcard/tests/xpc/m"; -f /sdcard/tests/xpc/head.js -e const _HEAD_FILES = ["/sdcard/tests/xpc/netwerk/test/unit/head_channels.js", "/sdcard/tests/xpc/netwerk/test/unit/head_cache.js", "/sdcard/tests/xpc/netwerk/test/unit/head_cache2.js", "/sdcard/tests/xpc/netwerk/test/unit/head_cookies.js"]; -e const _JSDEBUGGER_PORT = 0; -e const _TEST_FILE = ["test_bug1378385_http1.js"]; -e const _TEST_NAME = "netwerk/test/unit/test_bug1378385_http1.js"; -e _execute_test(); quit(0);
[task 2019-06-28T22:02:36.982Z] 22:02:36 INFO - Error: cannot open file '/sdcard/tests/xpc/netwerk/test/unit/head_channels.js' for reading at /sdcard/tests/xpc/head.js:637
[task 2019-06-28T22:02:36.983Z] 22:02:36 INFO - load_file@/sdcard/tests/xpc/head.js:637:7
[task 2019-06-28T22:02:36.983Z] 22:02:36 INFO - _load_files@/sdcard/tests/xpc/head.js:649:10
[task 2019-06-28T22:02:36.983Z] 22:02:36 INFO - _execute_test@/sdcard/tests/xpc/head.js:501:3
[task 2019-06-28T22:02:36.983Z] 22:02:36 INFO - @-e:1:1
[task 2019-06-28T22:02:36.983Z] 22:02:36 INFO - Error: cannot open file '/sdcard/tests/xpc/netwerk/test/unit/head_cache.js' for reading at /sdcard/tests/xpc/head.js:637
[task 2019-06-28T22:02:36.983Z] 22:02:36 INFO - load_file@/sdcard/tests/xpc/head.js:637:7
[task 2019-06-28T22:02:36.983Z] 22:02:36 INFO - _load_files@/sdcard/tests/xpc/head.js:649:10
[task 2019-06-28T22:02:36.984Z] 22:02:36 INFO - _execute_test@/sdcard/tests/xpc/head.js:501:3
[task 2019-06-28T22:02:36.984Z] 22:02:36 INFO - @-e:1:1
[task 2019-06-28T22:02:36.984Z] 22:02:36 INFO - Error: cannot open file '/sdcard/tests/xpc/netwerk/test/unit/head_cache2.js' for reading at /sdcard/tests/xpc/head.js:637
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - load_file@/sdcard/tests/xpc/head.js:637:7
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - _load_files@/sdcard/tests/xpc/head.js:649:10
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - _execute_test@/sdcard/tests/xpc/head.js:501:3
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - @-e:1:1
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - Error: cannot open file '/sdcard/tests/xpc/netwerk/test/unit/head_cookies.js' for reading at /sdcard/tests/xpc/head.js:637
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - load_file@/sdcard/tests/xpc/head.js:637:7
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - _load_files@/sdcard/tests/xpc/head.js:649:10
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - _execute_test@/sdcard/tests/xpc/head.js:501:3
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - @-e:1:1
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - Error: cannot open file 'test_bug1378385_http1.js' for reading at /sdcard/tests/xpc/head.js:637
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - load_file@/sdcard/tests/xpc/head.js:637:7
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - _load_files@/sdcard/tests/xpc/head.js:649:10
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - _execute_test@/sdcard/tests/xpc/head.js:503:3
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - @-e:1:1
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - (xpcshell/head.js) | test MAIN run_test pending (1)
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - (xpcshell/head.js) | test run_next_test 0 pending (2)
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - (xpcshell/head.js) | test MAIN run_test finished (2)
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - running event loop
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - (xpcshell/head.js) | test run_next_test 0 finished (1)
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - exiting test
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - netwerk/test/unit/test_bug1378385_http1.js | JavaScript error: resource://testing-common/PromiseTestUtils.jsm, line 110: uncaught exception: Object
[task 2019-06-28T22:02:36.986Z] 22:02:36 INFO - <<<<<<<

This likely started with the recent emulator update.

Corrected by downgrading the emulator used for android xpcshell tests, https://hg.mozilla.org/mozilla-central/rev/49f22f8f91f9, bug 1556058.