tomchristie/django-rest-framework — pull request #1272 by chuckharmston (2013-12-06 20:02:23+00:00)
Title: Raise appropriate error in serializer when making a partial update to set a required RelatedField to null (issue #1158)

Addresses issue #1158.

Uses the failing test casts from the issue report, updated to add two assertions to ensure that the correct error message is being served.