Missing reference results don't fail travis

[Mathadon]

I'm not sure whether this is intentional, but warnings like:

*** Warning: Reference file IDEAS_Buildings_Components_Examples_RectangularZoneEmbedded.txt does not yet exist.
Script that runs unit tests had 0 warnings and 0 errors.

do not cause travis to fail?

[mwetter]

That should fail with an error.