Fixed #10118 -- Clarified the error message raised when accessing a subclass...

However, if ``p`` in the above example was *not* a ``Restaurant`` (it had been

created directly as a ``Place`` object or was the parent of some other class),

referring to ``p.restaurant`` would give an error.

referring to ``p.restaurant`` would raise a Restaurant.DoesNotExist exception.

``Meta`` and multi-table inheritance

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