enable module

Hi,

When I enable any Drupal modules on the site it through following error message and site is not accessible after that:

“The website encountered an unexpected error. Please try again later”.

Following errors I found after hitting button and then look on the watchdog table.

1)Message Notice: Use of undefined constant user_access - assumed 'user_access' in field_indexer_menu() (line 16 of /home/drupal/ww/sites/all/modules/contrib/xmlsitemap/field_indexer/field_indexer.module).

Drush enable command for enabling modules requires some human intervention with input to type in Y/N when prompted. Is there any way to do it fully automatically through some api or script calls?