--- a/devtools/devctl.py	Tue Sep 15 18:43:19 2015 +0200
+++ b/devtools/devctl.py	Mon Oct 05 17:10:36 2015 +0200
@@ -84,7 +84,7 @@
 
 def cleanup_sys_modules(config):
     # cleanup sys.modules, required when we're updating multiple cubes
-    for name, mod in sys.modules.items():
+    for name, mod in list(sys.modules.items()):
         if mod is None:
             # duh ? logilab.common.os for instance
             del sys.modules[name]