The pre-test signal approach in the patch is no better than the appropach proposed in #5608. Test fixtures are applicable on a _per test_ basis.
However, I can accept the general use case you describe. I agree that it would be nice to be able to associate fixtures with a doctest without the need to insert the applicable code at the start of the test. I've modified the summary and description to reflect the underlying feature request, rather than the specific solution.
If you're looking at how to implement this, I would suggest looking at associating a fixtures attribute with the docstring itself, and modifying the Django doctest runner to look for the fixtures attribute.