Here's a patch:
1) the base class doesn't inherit from TestCase anymore -- the subclasses do;
2) added a skipUnless() decorator on the C subclass;
3) used the modern if __name__ == '__main__': unittest.main() idiom;
4) renamed the AcceleratedExampleTest to CExampleTest (I prefer the PyFoo/CFoo parallel, "Accelerated" doesn't necessarily imply that it's testing the C version);
5) added a paragraph to explain the idiom;
6) added Post-History;
7) did a couple of minor cleanup in the code;