Fix v0.3.0 incompatibility

Author: petertodd

examples/timestamp-op-ret.py

@@ -55,7 +55,7 @@
     change_pubkey = proxy.validateaddress(change_addr)['pubkey']
     change_out = CMutableTxOut(MAX_MONEY, CScript([change_pubkey, OP_CHECKSIG]))
 
-    digest_outs = [CMutableTxOut(0, CScript([script.OP_RETURN, digest]))]
+    digest_outs = [CMutableTxOut(0, CScript([OP_RETURN, digest]))]
 
     txouts = [change_out] + digest_outs