LDPSerializer: Key error with mismatched urlid

As of DjangoLDPv2.1 there will be a test in tests_model_serializer.py:

job = JobOffer.objects.create(title="job test")

# contains internal urlid which refers to a container
post = {"@id": "{}/job-offers/{}/".format(settings.BASE_URL, job.slug),
    "skills": {
        "ldp:contains": [
            {"@id": "{}/skills/".format(settings.BASE_URL)},
        ]}
}

serializer_class = self._get_serializer_class(JobOffer, 2, ("@id", "title", "skills"))
serializer = serializer_class(data=post, instance=job)
serializer.is_valid(raise_exception=True)
result = serializer.save()

Note that the skills resource here is intentionally a container rather than a valid url

Running this, the code makes it to build_nested_field, where it decides that it's a local resource (from the URL) and attempts to resolve the url. It raises a KeyError, relating to the fact that it is unable to resolve the correct url

Specification needed on what the correct behaviour should be (see #344), but in any case it's not "crash" 😁