Please correct this summary where it is technically wrong.
core/includes/install.inccontains (or was patched for current coding standards to contain):
PHP Warning: The use statement with non-compound name 'Exception' has no effect.
...but only when running tests. Not reproducible when manually testing the Drupal installer.
Furthermore, @jthorson manually ran the patch on scratchtestbot on PHP 5.3.3, and actually got a PHP fatal error instead of a warning there.
Removing one of the
use Exception;statements (doesn't matter which) resolves the error.
include_once DRUPAL_ROOT . '/core/includes/install.inc';
Change the coding standards to not import "global names"; i.e., native PHP classes.