App tests fail in Firefox 50.0

[dizzib]

Due to removal of marionette's global testUtils object which is used to maintain state across calls to _executeScript. Unfortunately I've been unable to find a substitute that works, having tried global, globals and window.

Possibly related issues:

https://bugzilla.mozilla.org/show_bug.cgi?id=1122583 https://bugzilla.mozilla.org/show_bug.cgi?id=1123506

Working configuration:

Firefox 45 marionette-client ~1.9.5