freezes the server (DEBUG version) with:
Just issue the expected message "Open error on e:/truc/foo.txt..."
Indeed the directory 'truc' does not exist on the disk E.
This may not be specific to the CONNECT engine. It seems that when the storage engine function write_row returns in error with rc= HA_ERR_INTERNAL_ERROR, the error return is handled correctly by MariaDB but in and only in the case of "CREATE TABLE ... AS SELECT ..." at the very end of the process, when the function Protocol::end_statement is called, the thd->get_stmt_da()->status() call returns an invalid value.
Things are almost worst when using a RELEASE server because the DBUG_ASSERT not being executed, no error message is displayed but the table is silently not created.