change error message to be more helpful.
change error message to be more helpful.

leungmanhin/relex,leungmanhin/relex,rodsol/relex,AmeBel/relex,linas/relex,virneo/relex,anitzkin/relex,williampma/relex,ainishdave/relex,leungmanhin/relex,williampma/relex,linas/relex,williampma/relex,anitzkin/relex,rodsol/relex,rodsol/relex,ainishdave/relex,rodsol/relex-temp,AmeBel/relex,rodsol/relex,opencog/relex,linas/relex,anitzkin/relex,ainishdave/relex,virneo/relex,virneo/relex,rodsol/relex-temp,rodsol/relex-temp,opencog/relex,rodsol/relex-temp,williampma/relex,anitzkin/relex,opencog/relex,AmeBel/relex,ainishdave/relex,rodsol/relex-temp,anitzkin/relex,virneo/relex