tests: improve test for `nose.raises`
tests: improve test for `nose.raises`

This should probably get transferred into a `pytest.fail` really, but
tests/documents the current behavior.

pytest-dev/pytest,nicoddemus/pytest,markshao/pytest,Akasurde/pytest,nicoddemus/pytest,RonnyPfannschmidt/pytest,alfredodeza/pytest,The-Compiler/pytest,The-Compiler/pytest