The 500 Service Unavailable error page is no longer shown

[atarix83]

Describe the bug
When the rest server is not available a 500 error page should be shown, currently in the main branch is no longer working and a blank page is shown instead

To Reproduce
Steps to reproduce the behavior:

1. configure the application in order to run over a not available rest server
2. run the application
3. a blank page is shown

Expected behavior
The Service Unavailable error page should be shown

Related work
#1498

[tdonohue]

Thanks for reporting this @atarix83 . I'll pull this over to the 7.4 board and flag as high priority. If you are interested in helping fix it, let me know. Not sure offhand what could have caused it.

[artlowel]

I have a hunch it could be caused by the shibboleth work. We'll take a look

[tdonohue]

@artlowel : Thanks, sounds good. I'll assign you to it then.