Given that all of rspec-core is always loaded in our specs, it's safer to use `instance_double(Exception, ...)` rather than `instance_double("Example", ...)` because if you use a string and typo it, the instance double will just think the named constant hasn't been loaded and won't verify anything.

Actually, I just realized that this isn't actually verifying anything, because the constant name is "RSpec::Core::Example", but you just passed "Example". I recommend passing the constant itself though, as it's safer.