Don't mine txs with unconfirmed parents

Reduces risk of creating invalid blocks

p2pool/bitcoin/helper.py

@@ -55,7 +55,7 @@ def go():
         except jsonrpc.Error_for_code(-32601): # Method not found
             print >>sys.stderr, 'Error: Bitcoin version too old! Upgrade to v0.5 or newer!'
             raise deferral.RetrySilentlyException()
-    packed_transactions = [(x['data'] if isinstance(x, dict) else x).decode('hex') for x in work['transactions']]
+    packed_transactions = [x['data'].decode('hex') for x in work['transactions'] if len(x.get('depends', [])) == 0]
     if 'height' not in work:
         work['height'] = (yield bitcoind.rpc_getblock(work['previousblockhash']))['height'] + 1
     elif p2pool.DEBUG: