Remove unused or redundant imports in concurrent.futures and multiprocessing.
diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
index fbac088..95bb682 100644
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -74,7 +74,7 @@
                 work_queue.put(None)
                 return
             del executor
-    except BaseException as e:
+    except BaseException:
         _base.LOGGER.critical('Exception in worker', exc_info=True)
 
 class ThreadPoolExecutor(_base.Executor):