Improve error messages from NodeNorm

[gaurav]

Suggestions for improvement:

• There are a bunch of places in NodeNorm where exceptions are trapped and then not reported correctly; these should be fixed.
• @YaphetKG has reported that when the Redis servers are having issues, it's often unclear where the error is originating from. Something like "No results returned from id-categories" or something would be helpful in figuring out which server is incorrectly loaded.