- SFTP a file called secrets.json to your D8's files/private folder.
- Just put this in the file to make a legit json file: {}
- In your D8 site's settings.php put this at the bottom:
# When on Pantheon, connect to a D7 database.
$migrate_settings = __DIR__ . "/settings.migrate-on-pantheon.php";
if (file_exists($migrate_settings) && isset($_ENV['PANTHEON_ENVIRONMENT'])) {