Fix cryptic errors when tests_json_path is missing ref_config
Fix cryptic errors when tests_json_path is missing ref_config

weeksghost/dpxdt,steven-hadfield/dpxdt,mabushadi/dpxdt,gBritz/dpxdt,mabushadi/dpxdt,Medium/dpxdt,Medium/dpxdt,weeksghost/dpxdt,bslatkin/dpxdt,steven-hadfield/dpxdt,ygravrand/dpxdt,gBritz/dpxdt,steven-hadfield/dpxdt,mabushadi/dpxdt,gBritz/dpxdt,mabushadi/dpxdt,gBritz/dpxdt,ygravrand/dpxdt,weeksghost/dpxdt,Medium/dpxdt,bslatkin/dpxdt,ygravrand/dpxdt,bslatkin/dpxdt,ygravrand/dpxdt,weeksghost/dpxdt,Medium/dpxdt,steven-hadfield/dpxdt,bslatkin/dpxdt