make warnings more readable in Index.parse
make warnings more readable in Index.parse

orangain/review,krororo/review,kmuto/review,kuad9/review_study,murashitas/review,masawada/review,suzuki/review,takahashim/review,kmuto/review,orangain/review,masawada/review,krororo/review,murashitas/review,kuad9/review_study,krororo/review,kmuto/review,takahashim/review,suzuki/review