Installer falls into indefinite loop if SQL error/exception is thrown in migration. It doesn't stop executing and continues endless creating migration log files in the /store folder.

If, for example, this kind of error is thrown

General Error:SQL ERROR [ mysqli ]BLOB/TEXT column 'my_column' used in key specification without a key length [1170]SQLALTER TABLE phpbb_tests ADD INDEX my_index (my_column) in file [ROOT]\phpbb\db\driver\driver.php on line 1031

then 3.3.x installer stops executing and shows actual error while 4.0.0 installer doesn't and just hangs while executing forever in the background.