fixing changed set during iteration

xtreemfs_client/div_util.py

@@ -41,12 +41,14 @@ def run_commands(commands, max_processes=200):
         running_processes.add(started_process)
         if len(running_processes) >= max_processes:
             os.wait()
+            difference = set()
             for running_process in running_processes:
                 if running_process.poll() is not None:
-                    finished_processes.append((running_process.args,
+                    difference.add((running_process.args,
                                                running_process.communicate(),
                                                running_process.returncode))
-                    running_processes.remove(running_process)
+            running_processes = running_processes.difference(difference)
+            
 
     for p in running_processes:
         p.wait()