PHP Fatal error: Call to undefined function system_schema()

On uninstall of the Releases module, the following Fatal error happens.
PHP Fatal error: Call to undefined function system_schema()

Loading of the systems cache schema, should be updated to use the drupal_get_schema_unprocessed() function instead.

$schema['cache_project_release_download_table'] = drupal_get_schema_unprocessed('system', 'cache');