The basic logger's "levels"
of output don't really apply here. I at least want categories, if not
hierarchical sub-categories.
Python's built-in logging has a hierarchy of loggers according to the name - you can set up log handling for the logger named 'foo', and things from the logger 'foo.bar' will go to that. The convention is to instantiate each logger with a module name, so you can configure logging by package, but I think you could use it with any hierarchy.
It is text-only, as far as I know, but it might save you some work.