update test_readers to assert FileNotFoundError thrown on missing file
update test_readers to assert FileNotFoundError thrown on missing file

zhwa/thunder,zhwa/thunder,kunallillaney/thunder,broxtronix/thunder,pearsonlab/thunder,mikarubi/thunder,pearsonlab/thunder,jwittenbach/thunder,broxtronix/thunder,j-friedrich/thunder,oliverhuangchao/thunder,kunallillaney/thunder,oliverhuangchao/thunder,j-friedrich/thunder,kcompher/thunder,poolio/thunder,kcompher/thunder,thunder-project/thunder,mikarubi/thunder,poolio/thunder