How can I debug white screen when running install script? I'm doing a fresh install of drupal7 on Ubuntu following these instructions.

When I get to the point of running the install script (by pointing the browser at localhost/drupal7/install.php) it just gives a blank screen.

Most questions/help about the Drupal blank screen relate to site setup but as this is a new install, I haven't created any sites yet so am unable to figure out what to do.

Does anyone know how to debug or move past this issue?
You can edit your settings.php file and add

ini_set("display_error" , 1);