The deprecation library provides a deprecated decorator and a
fail_if_not_removed decorator for your tests. Together, the two enable the
automation of several things:
- The docstring of a deprecated method gets the deprecation details appended to
  the end of it. If you generate your API docs direct from your source, you
  don't need to worry about writing your own notification. You also don't need
  to worry about forgetting to write it. It's done for you.
- Rather than having code live on forever because you only deprecated it but
  never actually moved on from it, you can have your tests tell you when it's
  time to remove the code. The @deprecated decorator can be told when it's time
  to entirely remove the code, which causes @fail_if_not_removed to raise an
  AssertionError, causing either your unittest or py.test tests to fail.