Use nose tools to check for exceptions

Some of our tests checked for exceptions using an error-prone
try block: they allowed the expected exception to pass, but sometimes
forgot an else block, so the test passed when an exception wasn't
thrown.

This changes the tests to use the appropriate nose tools (raises,
assert_raises).
For consistency, tests that had a correct else block are also changed.

Also fix some test problems that were hidden by the above:
- in some sudorule and HBAC tests, change the *_add_user argument name
  from `users` to `user`
- don't remove HBAC testing data while it was still used

0 files changed, 0 insertions, 0 deletions