SQLite fails 100% of time on Drupal\migrate_drupal_ui\Tests\d6\MigrateUpgrade6Test and Drupal\migrate_drupal_ui\Tests\d7\MigrateUpgrade7Test

Running locally the exception is thrown with
SQLSTATE[HY000] [14] unable to open database file
/Volumes/devdisk/dev/sites/drupal8alt.dev/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php line 120...

So this is now not happening on testbot for some reason.

So if you do

    $connection_options = array(
      'database' => '/wrong',
      'pdo' => array(),
    );
    $connection_options['pdo'] += array(
      \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
      // Convert numeric values to strings when fetching.
      \PDO::ATTR_STRINGIFY_FETCHES => TRUE,
    );

    $pdo = new \PDO('sqlite:' . $connection_options['database'], '', '', $connection_options['pdo']);

On a testbot then it'll write a file "wrong" to the root directory. Basically php can write anywhere on the disk. This must have been part of the recent permission changes.

The attached patch passes on a local DrupalCI and running the test without DrupalCI.

This fail was caused by a change in permissions on DrupalCI. This change has been reverted so for now this has been fixed by #2841024: Investigate overly permissive permission issues in containers.

This is happening again. Whilst we could go with #4 I don't think that that is good option because that'd just be hiding a permissions error.