This found a small number of real bugs too, for example,
this one that looked weird because of a 2to3 conversion,
but was wrong both before and after:
-        except IndexError as TypeError:
+        except (IndexError, TypeError):

Also fix a bug when reporting bad units on "keep" configuration key

This is instead of hardcoding 500

Cherrypy uses a bunch of globals, so use multiprocessing to let us
spawn a few that are totally independent.

Might fix the problem Mark noticed where turn-off transients
are erroneously matching the drop that follows startup transients.