Fix change value calculation when using alternating asset inputs

CHANGELOG.rst

@@ -16,6 +16,7 @@ All notable changes to this project are documented in this file.
 - Add fix to ensure tx is saved to wallet when sent using RPC
 - Add bad peers to the ``getpeers`` RPC method `#715 <https://github.com/CityOfZion/neo-python/pull/715>`
 - Allow a raw tx to be build without an active blockchain db in the environment
+- Fix calculation of asset change value when using multiple alternating asset inputs
 
 
 [0.8.2] 2018-10-31

neo/Wallets/Wallet.py

@@ -1032,7 +1032,8 @@ def MakeTransaction(self,
                 sum = Fixed8(0)
                 for item in group:
                     sum = sum + item.Value
-                paytotal[key] = sum
+                cur_val = paytotal.get(key, Fixed8.Zero())
+                paytotal[key] = cur_val + sum
         else:
             paytotal = {}