Minor tweak to convert script

convert.py

@@ -3,7 +3,7 @@
 
 The json output will look like this:
 {
-    "AF12345678": { <<--- all uppercase letter of the name + username/matrikel_no
+    "max.mustermann": { <<--- OR all uppercase letter of the name + username/matrikel_no
         "matrikel_no": "12345678",
         "name": "Mustermann, Max",
         "task_list": {
@@ -105,7 +105,6 @@ if args.NUMBER_OF_TASKS:
     for (user, *task_list) in sorted(root, key=lambda u: u[0].name):
         assert len(task_list) == args.NUMBER_OF_TASKS * 2
 
-usernames = {}
 if args.usernames:
     with open(args.usernames) as data:
         mat_to_email = json.JSONDecoder().decode(data.read())