trust built-in if its available

diff --git a/requests/packages/urllib3/_collections.py b/requests/packages/urllib3/_collections.py
index 912c866..ccc3973 100755 (executable)
--- a/requests/packages/urllib3/_collections.py
+++ b/requests/packages/urllib3/_collections.py
@@ -8,7 +8,10 @@
 from collections import deque
 from threading import RLock
 
-from .__collections import MutableMapping
+try:
+    from collections import MutableMapping
+except ImportError:
+    from .__collections import MutableMapping
 
 __all__ = ['RecentlyUsedContainer']