Make a copy of the topic list

get_topics() returns a set, which is iterated by the Log constructor.
Make a copy of the set (atomic in cpython!) so nobody adds or removes
something while the Log constructor iterates over it

clients/rospy/src/rospy/impl/rosout.py

@@ -95,7 +95,7 @@ def _rosout(level, msg, fname, line, func):
                         disable_topics_ = False
 
                     if not disable_topics_:
-                        topics = get_topic_manager().get_topics()
+                        topics = get_topic_manager().get_topics().copy()
                     else:
                         topics = ""