* This method should be called ONLY when you load up a _legacy_ attribute using _legacy_ attribute store! Basically
* it "repacks" the deprecated fields as loaded by XStream (as back then XStream was used to serialize Item instances)
* into new Attributes.
*/
public void upgrade() {
this.context = new RequestContext();
this.itemAttributes = new DefaultAttributes();
// this here is for ITs only, some of them use "manually crafter" attributes XML files and would NPE
// In "real life", all the files stored in Nexus have at least sha1/md5 set as attributes, meaning,
// all the real life items has at least two attributes and this map would never be null!