If you have an external, non-ACID table and try to upgrade it to become an ACID table you get an error message that an external table is not allowed to be promoted to ACID. This is fine, however if in the very same step you set 'EXTERNAL' = 'FALSE' in table properties you still get the same error while Hive is able to execute it.
Steps to repro:
1) Create a non-ACID external table. (or a single non-ACID table if you use Hive that contains
2) Upgrade the table
Step 2) fails in Impala but succeeds in Hive