cubicweb #2374368 Half of the thread are not joined during repository shutdown [open]

The content of the loop alter the list break iteration

439         for thread in self._running_threads:
440             self.info('waiting thread %s...', thread.getName())
441             thread.join()
442             self.info('thread %s finished', thread.getName())
priorityimportant
typebug
done in<not specified>
load0.250
load left0.250
closed by<not specified>