hook_apps_app_info post install callback never called.

I have define the following in my module, as per the documentation. How ever the post install callback is never called -> sac_chapter_affiliation_app_post_install.

/**
 * Implements hook_apps_app_info().
 */
function sac_chapter_affiliation_apps_app_info() {
  return array('post install callback' => 'sac_chapter_affiliation_app_post_install');
}

/**
 * Helper function to run post app installation configuration.
 */
function sac_chapter_affiliation_app_post_install() {
  dsm('sac_chapter_affiliation_app_post_install');
  // We do this here and not in the install hook as when the install hook runs
  // the vocabulary sac_affiliation_types does not yet exist.
  $vocabulary_name = 'sac_affiliation_types';
  $vocabulary = taxonomy_vocabulary_machine_name_load($vocabulary_name);

  // Add default vocabulary term
  $term = new stdClass();
  $term->name = 'individual affiliations';
  $term->vid = $vocabulary->vid;
  $term->vocabulary_machine_name = $vocabulary->machine_name;
  $term->parent = array(0);
  taxonomy_term_save($term);

  // Add default vocabulary term
  $term = new stdClass();
  $term->name = 'corporate affiliations';
  $term->vid = $vocabulary->vid;
  $term->vocabulary_machine_name = $vocabulary->machine_name;
  $term->parent = array(0);
  taxonomy_term_save($term);
}