fix code after rebase

Author: glevco

tests/tx/test_mining.py

@@ -2,8 +2,8 @@
 
 from hathor.conf import HathorSettings
 from hathor.mining import BlockTemplate
-from hathor.transaction import Block, sum_weights
 from hathor.simulator.utils import add_new_blocks
+from hathor.transaction import Block, sum_weights
 from hathor.transaction.storage import TransactionMemoryStorage
 from tests import unittest