I'm following the instructions found here to create an offline Transaction. When executing, the following line, I get "Can only serialize integers" exception raised by rlp. I did import pdb;pdb.pm() and the address is a string, not an integer (obviously). Any idea what's going on?
t = ethereum.transactions.Transaction(nonce, 60 * 10**9, 21000, to, value, '').sign(k)