File _constraints of Package HepMC

<?xml version="1.0" encoding="UTF-8"?>
<constraints>
  <hardware>
    <memory>
      <size unit="G">2</size>
    </memory>
    <disk>
      <size unit="G">4</size>
    </disk>
    <memoryperjob>
      <size unit="M">1536</size>
    </memoryperjob>
  </hardware>
</constraints>