generatefeed.py: remove useless items instead of crashing

Until now, if json item files couldn't be read, the script was
crashing. This commit delete the corrupted files as they do not
provide any useful information.

slapos/generatefeed.py

@@ -64,7 +64,12 @@ def generateFeed(option):
   for filename in os.listdir(option.status_item_path):
     file_path = os.path.join(option.status_item_path, filename)
     with open(file_path, 'r') as fd:
+      try:
         item_dict[file_path] = json.load(fd)
+      except ValueError:
+        # JSON couldn't be decoded, let's trash it as
+        # no useful information can be extracted
+        os.unlink(file_path)
 
   sorted_item_dict = collections.OrderedDict(
       sorted(item_dict.items(), key=lambda x: x[1]['pubDate']))