add check whether updated folders are known in the dataDistribution

xtreemfs_client/dataDistribution.py

@@ -533,10 +533,13 @@ class DataDistribution(object):
         """
         updates the size of a given folder
         """
+        found_containing_osd = False
         for one_osd in self.OSDs.values():
             if folder in one_osd.folders.keys():
                 one_osd.update_folder(folder, size)
+                found_containing_osd = True
                 break
+        assert found_containing_osd is True
 
     def description(self):
         """