message: Add file validation to savemempool RPC test
diff: @@ -149,8 +149,9 @@ class MempoolPersistTest(BitcoinTestFramework):
  mempooldat1 = os.path.join(self.nodes[1].datadir, self.chain, 'mempool.dat')
  self.log.debug("Remove the mempool.dat file. Verify that savemempool to disk via RPC re-creates it")
  os.remove(mempooldat0)
  - self.nodes[0].savemempool()
  + result0 = self.nodes[0].savemempool()
  assert os.path.isfile(mempooldat0)
  + assert_equal(result0['filename'], mempooldat0)
  self.log.debug("Stop nodes, make node1 use mempool.dat from node0. Verify it has 6 transactions")
  os.rename(mempooldat0, mempooldat1)
  