Patch attached.

No docs, if it is agreed I can apply I'll write docs.

After a long discussion we arrived at some semblance of consensus on the
Testing In Python mailing list that this was a good thing (tm).

Only one -1 (thought that cleanUp should be a method) and Holger Krekel
was only +0 because he thinks changes in unittest should be conservative
(but he isn't actually using it).

Many others were +1 - Fred Drake, Titus Brown, Laura Creighton, Robert
Collins, Jonathan Lange, Kumar McMillan and others.

It provides a clean and simple pattern for the cleaning up of resources
- avoiding the need for nested try finallys and the manual tracking of
resources. It can also avoid the need for duplication of cleanup code.