Add error context while evaluating predicates
Add error context while evaluating predicates

jwakely/ledger,paulbdavis/ledger,ledger/ledger,duncanmortimer/ledger,duncanmortimer/ledger,jwakely/ledger,paulbdavis/ledger,jwakely/ledger,paulbdavis/ledger,paulbdavis/ledger,afh/ledger,duncanmortimer/ledger,ledger/ledger,jwakely/ledger,duncanmortimer/ledger,ledger/ledger,duncanmortimer/ledger,ledger/ledger,afh/ledger,afh/ledger,afh/ledger,jwakely/ledger,duncanmortimer/ledger,jwakely/ledger,ledger/ledger,duncanmortimer/ledger,paulbdavis/ledger,paulbdavis/ledger,paulbdavis/ledger,afh/ledger,jwakely/ledger