Bug 20767: Display a stack trace when a method is not covered by tests

Bug 20767: Display a stack trace when a method is not covered by tests

When a method is not allowed yet (not covered by tests), developers get
an error the is not really useful: "The method XXX is not covered by
tests!"
It would be more useful to have a stack trace in order to know where
this error come from.

Test plan:
Modify some code to display this stack trace and confirm it makes sense
to have it, i.e. it will make debug easier

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>