message: Tests: fixup a conditional check for python block creation
diff: @@ -494,7 +494,7 @@ class CBlock(CBlockHeader):
  r += ser_vector(self.vtx, "serialize_with_witness")
  else:
  r += ser_vector(self.vtx, "serialize_without_witness")
  - if self.vchBlockSig:
  + if hasattr(self, 'vchBlockSig'):
  r += ser_string(self.vchBlockSig)
  return r
  