Difference of behavior in assertRaises when used as context manager

[stephenfin]

assertRaises can be used as a context manager since 2.8.0 (#443). However, the behavior is different (and IMO inferior) to the unittest behavior. For example, with unittest:

with self.assertRaises(BazException) as exc:
    foo('a', 'b', bar=123)

self.assertIn('baz thing', str(BazException))

This is not possible since exc is an instance of _AssertRaisesContext rather than the exception we've captured. To access the exception, I believe we need to use the .exception attribute.

[stephenfin]

fwiw, I'm happy to work on this. Before I do though, I'm wondering if it's possible to change the return type? We could likely use setattr to set a deprecated exception attribute on the captured exception, but I wonder if it'd be possible instead of release note this on the assumption that not a lot of people are actually using this yet?