add backup

dropbox-script/urllib3/util/queue.py

@@ -0,0 +1,21 @@
+import collections
+from ..packages import six
+from ..packages.six.moves import queue
+
+if six.PY2:
+    # Queue is imported for side effects on MS Windows. See issue #229.
+    import Queue as _unused_module_Queue  # noqa: F401
+
+
+class LifoQueue(queue.Queue):
+    def _init(self, _):
+        self.queue = collections.deque()
+
+    def _qsize(self, len=len):
+        return len(self.queue)
+
+    def _put(self, item):
+        self.queue.append(item)
+
+    def _get(self):
+        return self.queue.pop()