I am not sure of the root cause here, but I tried to run the following: $ ./mach try -b do -p linux64,macosx64,win32,win64 --rebuild 10 devtools/client/responsive.html/test/browser which gave the try run: https://treeherder.mozilla.org/#/jobs?repo=try&revision=9e8c210822eb854f0fe3fec0dbae5151090acf01 But all of the Linux jobs (and presumably others, but I cancelled it before then...) skipped all of the tests: https://treeherder.mozilla.org/logviewer.html#?job_id=71651011&repo=try Maybe this is something specific to the DevTools mochitest-browser subsuite?

Oh, maybe the issue here is that these tests don't run when e10s is disabled, and the runs with errors are e10s off runs... I guess I'll need to manually restrict to e10s runs only.