Form submit catch error tests failing for Embroider

[simonihmig]

Even without any explicit dependency update, since some days these two tests added in #1581 are failing for Embroider scenarios. See this scheduled run which is failing, compared to the scheduled run a week earlier which is passing.

In those tests the callback to setupOnerror() (which delegates to Ember.onError) is indeed not called, no idea why. The scenario adds the embroider dependencies and webpack, so my assumption is some recent updates to those dependency were causing this. I tried to track this down by pining embroider or webpack dependencies down to earlier versions, but that did not succeed. Those tests are still failing, so maybe related to some transitive dependencies?

cc @jelhan @ef4