I haven't been able to duplicate the failures locally, but I've updated the patch and am giving it another shot on try.
Bug 1724985 Comment 5 Edit History
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I haven't been able to duplicate the failures locally, but I've updated the patch and am giving it another shot on try. EDIT: We found the issue, it had to do with the difference in path handling between platforms. I have a new patch up waiting to land; I'm still seeing a single failure on try but it looks like a known intermittent: https://treeherder.mozilla.org/push-health/push?repo=try&revision=6acf390a90a253271ed17838a2102acc73611f7f&tab=tests&testGroup=pr&selectedTest=browserbasecontenttestformsbrowserselectpopupjs&selectedTaskId=357390706&selectedJobName=browser%2Fbase%2Fcontent%2Ftest%2Fforms%2Fbrowser_selectpopup.js+test-windows10-64-2004-qr%2Fopt-mochitest-browser-chrome-fis-e10s-5