Oracle Message ORA-14064 - Index with Unusable partition exists on unique/primary constraint key

ERRORIndex with Unusable partition exists on unique/primary constraint key
CAUSEUser attempted to add or enable a primary key/unique constraint on column(s) of a table on which there exists an index one or more partitions of which are marked Index Unusable.
ACTIONDrop the existing index or rebuild unusable partitions it using ALTER INDEX REBUILD PARTITION