public function userCanChangePrioritiesInMilestone(Planning_ArtifactMilestone $milestone, PFUser $user)
 {
     $planning = $milestone->getPlanning();
     $user_can_change_priorities = $this->planning_permissions_manager->userHasPermissionOnPlanning($planning->getId(), $planning->getGroupId(), $user, PlanningPermissionsManager::PERM_PRIORITY_CHANGE);
     if (!$user_can_change_priorities && $milestone->hasAncestors()) {
         return $this->userCanChangePrioritiesInMilestone($milestone->getParent(), $user);
     }
     return $user_can_change_priorities;
 }