bugfix to assertRaises, add suffix to mkstemp, remove unused 'rm'
remove unused safe_repr, skip_if
remove 'safe_repr' usage
adding assertRaises/assertRaisesRegexp with context management
switching tests over to assertRaises context manager
skip assertRaises in optimized mode
Merge pull request #98 from pyfarm/assertRaises_context

Context Manager for assertRaises/assertRaisesRegexp