It is not very clear why this code exists -- we are not running any
unittest or nose code during collection, and really these frameworks
don't have the concept of collection at all, and just raising these
exceptions at e.g. the module level would cause an error. So unless I'm
missing something, I don't think anyone is using this.
Deprecate it so we can eventually clear up this code and keep unittest
more tightly restricted to its plugin.
Ran Benita