user_admin_access_check_validate($form_id, $form_values)
user/user.module, line 1619
<?php
function user_admin_access_check_validate($form_id, $form_values) {
if (empty($form_values['test'])) {
form_set_error($form_values['type'], t('No value entered. Please enter a test string and try again.'));
}
}
?>