Fix error message more specifically. Ref #214.
Fix error message more specifically. Ref #214.

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