Debug headers missing in case of a 500

[kptdobe]

Trickiest part is that the HTML action should fire a 500. I assume putting a throw new Error() in the pre.js should do the trick but I did not test it.

• Ensure that page renders a 500 from Fastly.
• Enable the X-Debug hearder with the corresponding service id.

-> 50% of the debug headers are missing compared to a working page. And a key header like x-openwhisk-activation-id is missing which is crucial for debugging in that case...

[trieloff]

I think this is a helix-dispatch issue. If the html action returns an error 500, the standard fallback processing comes into place, which delivers the 404.html page.