Fix Exception Messages

While trying to get ros_acomms running in simulation, I hit a number of exceptions whose error messages also triggered exceptions. This PR addresses the ones that I encountered.

Also changed variable name 'id' in packet_dispatch_node since that's also the name of a built-in function.

(My editor strips trailing whitespace, so there are some lines where only that changed.)

In order to get this merged into master, I assign copyright to Woods Hole Oceanographic Institution.