Documented behavior of get_or_create when multiple objects are returned.

Any keyword arguments passed to ``get_or_create()`` — *except* an optional one

called ``defaults`` — will be used in a :meth:`get()` call. If an object is

found, ``get_or_create()`` returns a tuple of that object and ``False``. If an

object is *not* found, ``get_or_create()`` will instantiate and save a new

object, returning a tuple of the new object and ``True``. The new object will

be created roughly according to this algorithm::

found, ``get_or_create()`` returns a tuple of that object and ``False``. If

multiple objects are found, ``get_or_create`` raises

:exc:`~django.core.exceptions.MultipleObjectsReturned`. If an object is *not*

found, ``get_or_create()`` will instantiate and save a new object, returning a

tuple of the new object and ``True``. The new object will be created roughly

according to this algorithm::

    defaults = kwargs.pop('defaults', {})

    params = dict([(k, v) for k, v in kwargs.items() if '__' not in k])