Bad error message when non-ACID files are put in an insert_only ACID table

I created an insert_only transactional table, and then dropped a text file into the table's directory from a non-transaction-aware client. When I next queried the table, I got the following error:

Error: java.io.IOException: java.io.IOException: Not a file: hdfs://localhost:20500/test-warehouse/trans/delta_0000002_0000002_0000 (state=,code=0)

It seems that Hive saw the non-ACID file and fell back to some kind of non-ACID reader path, but then got confused by the delta directory. This case should either fall back to gracefully reading the file, or give an error message like "Unexpected file not conforming to ACID layout: <path>. Data must be loaded using into transactional tables LOAD DATA." or something.