Why does exception not return the actually raised error?

I'm getting my function tomato_or_potato() to fail for testing as in potato check

def potato_check:
    if not potato:
        raise SpecificError(
            message='No potato.',
            status_code=409,
        )

In my test, I'm trying to assert that SpecificError was raised:

    with assertRaises(Exception) as context:
        tomato_or_potato(tomato)

    assert SpecificError in context.exception

What I'm getting back tho is always a message 'No potato.' and not the actual SpecificError.