src/main/java/com/conveyal/gtfs/validator/Validator.java
public void registerError(Entity entity, NewGTFSErrorType errorType, Object badValue) {
        errorStorage.storeError(NewGTFSError.forEntity(entity, errorType).setBadValue(badValue.toString()));
    }
public void registerError(Entity entity, NewGTFSErrorType errorType, Object badValue) {
        errorStorage.storeError(NewGTFSError.forEntity(entity, errorType).setBadValue(badValue.toString()));
    }
Store an error that affects a single line of a single table.
Add a bad value to it.