public function getMember(Project $project, $id)
 {
     if (!ctype_digit($id)) {
         throw new ModelException('Invalid user ID');
     }
     $this->transaction->requestTransaction();
     $user = $project->findMember($this->conn, $this->roleResolver, $id);
     if (empty($user)) {
         throw new ItemNotFoundException('The specified user has not been found.');
     }
     return $user;
 }