Add error handling of exception thrown during accumulation

[WilliamParker]

#255 added information to most exceptions thrown in LHS rule conditions. However, it does not handle exceptions thrown inside accumulators. The types of information most meaningful to accumulator errors likely vary from that for exceptions that arise from constraints, but we should be able to reuse the functionality that was added there for gathering information on the condition(s) that correspond to a node and the rules that they ultimately feed into.