Comment 3 for bug 1456353

I wanted to capture the logic here for easy later review..., so I did a blog post. https://rbtcollins.wordpress.com/2015/06/22/revisiting-the-fixture-api-handling-leaky-resources/

This particular bug is invalid: useFixture isn't and shouldn't be responsible for figuring out the right way to deal with a failed fixture: since we need to solve the with: case, there's no need for the useFixture code to be any different to with:, other than that its spread out over two call sites.