It is wrong to compare keys, as ordering is unspecified. Use sorted instead

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@42220 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/BalanceTransaction.py

@@ -67,7 +67,7 @@ class InventoryKey(UserDict):
   def __cmp__(self, other):
     # this is basically here so that we can see if two inventory keys are
     # equals.
-    if tuple(self.keys()) != tuple(other.keys()):
+    if sorted(self.keys()) != sorted(other.keys()):
       return -1
     for k, v in self.items():
       if v != other[k]: