Right now, it only warns and continues. While this might mean 'there already exists a resource with the value we need for the test', this is really hiding a design issue with the tests.

For example

```perl
my $library = $builde->build_object(
    {
        class => 'Koha::Libraries,
        value => { branchcode => 'ILL', pickup_location => 1 }
    }
);
```

might fail because 'ILL' already exists, but if the DB entry doesn't contain the other fixed condition (pickup_location=1) then the tests could fail weirdly, and tracking it would be harder (i.e. you read the code, see you are setting pickup_location=1, but it fails because it is not).

I propose we make it explode loudly instead. And fix the poorly written tests that explode because of it.