Fix python3.7 unittest failure
In python3.7 unittest, there is a failure that the dictionary changed size
during iteration, so fixing it by list instead of dict.
@@ -465,7 +465,7 @@ class ExtensionManager(object):
# is made in a whole iteration
while exts_to_process:
processed_ext_count = len(processed_exts)
- for ext_name, ext in exts_to_process.items():
+ for ext_name, ext in list(exts_to_process.items()):
if not hasattr(ext, 'get_extended_resources'):
del exts_to_process[ext_name]
continue
