Fix #15567. collections.deque wasn't imported

Lib/threading.py

@@ -10,6 +10,7 @@ except ImportError:
 
 import warnings
 
+from collections import deque as _deque
 from time import time as _time, sleep as _sleep
 from traceback import format_exc as _format_exc
 
@@ -913,7 +914,7 @@ def _test():
             self.rc = Condition(self.mon)
             self.wc = Condition(self.mon)
             self.limit = limit
-            self.queue = deque()
+            self.queue = _deque()
 
         def put(self, item):
             self.mon.acquire()