fix ValueError argument in Multihash constructor

Author: ivilata

multihash.py

@@ -46,7 +46,7 @@ def __new__(cls, func, length, digest):
         try:
             f = Func(func)
         except ValueError as ve:
-            raise ValueError("invalid hash function code", f)
+            raise ValueError("invalid hash function code", func)
         return super(cls, Multihash).__new__(cls, f, length, digest)