The test fails on this:

def g():
    try:
        return g()
    except ValueError:
        return -1
self.assertRaises(RuntimeError, g)


Changing that "return -1" to "return sys.exc_info()" shows that a
RuntimeError was raised indeed. Also, using TypeError or TabError
instead of ValueError gives the same result.

Shallow testing of the new methods seem to show normal results,

[Runtime,Value]Error.__[subclass,instance]check__([Runtime,Value]Error)

is False for cross-checks and True otherwise.