I discovered that my catch all exception handling had a very nasty side-effect: inability the stop the script from running with Ctrl+C.  In fact the way I was able to get it to stop was to upload an empty main.py and reboot it.  I did a bit of searching and asked on the MicroPython forum about specifically catching OneWire exceptions and someone provided a working solution: "except onewire.OneWireError:"

I've since added another DS18B20+ on a separate I/O pin to monitor the indoor temperature. I've added an additional field that calculates the difference between indoor/outdoor, but I may remove that in the future as that can of course be calculated in a spreadsheet program. An interesting thing about monitoring the temperature inside is that one can see when HVAC is running by observing the sawtooth pattern in the graph below generated by the temperature reading logs(red line is indoor temperature, blue is the attic temperature.)