ReferenceError is undefined.  causes test___all__.py to fail.  remove it from __all__
diff --git a/Lib/weakref.py b/Lib/weakref.py
index 3301070..64d962c 100644
--- a/Lib/weakref.py
+++ b/Lib/weakref.py
@@ -25,7 +25,7 @@
 ProxyTypes = (ProxyType, CallableProxyType)
 
 __all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
-           "WeakKeyDictionary", "ReferenceError", "ReferenceType", "ProxyType",
+           "WeakKeyDictionary", "ReferenceType", "ProxyType",
            "CallableProxyType", "ProxyTypes", "WeakValueDictionary",
            "WeakSet"]