test: Use clean chain in MempoolCompatibilityTest

The test creates enough blocks itself, so there is no need to have more.

Also, remove os import.

Author: MarcoFalke

test/functional/mempool_compatibility.py

@@ -10,8 +10,6 @@
 Previous releases are required by this test, see test/README.md.
 """
 
-import os
-
 from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.wallet import (
@@ -23,6 +21,7 @@
 class MempoolCompatibilityTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
+        self.setup_clean_chain = True
 
     def skip_test_if_missing_module(self):
         self.skip_if_no_previous_releases()
@@ -55,9 +54,9 @@ def run_test(self):
         self.stop_node(1)
 
         self.log.info("Move mempool.dat from old to new node")
-        old_node_mempool = os.path.join(old_node.chain_path, 'mempool.dat')
-        new_node_mempool = os.path.join(new_node.chain_path, 'mempool.dat')
-        os.rename(old_node_mempool, new_node_mempool)
+        old_node_mempool = old_node.chain_path / "mempool.dat"
+        new_node_mempool = new_node.chain_path / "mempool.dat"
+        old_node_mempool.rename(new_node_mempool)
 
         self.log.info("Start new node and verify mempool contains the tx")
         self.start_node(1)
@@ -70,7 +69,7 @@ def run_test(self):
         self.stop_node(1)
 
         self.log.info("Move mempool.dat from new to old node")
-        os.rename(new_node_mempool, old_node_mempool)
+        new_node_mempool.rename(old_node_mempool)
 
         self.log.info("Start old node again and verify mempool contains both txs")
         self.start_node(0, ['-nowallet'])