api-listen: Fix gossip snapshot assertions

- Use assert_called_with instead of assert called_with to avoid the
  AttributeError thrown by Python 3.12.
- Use different names for the snapshot files tested on the test_gossip
  and test_gossip_with_dest test cases in case the two tests run
  simultaneously. In this case, the listener would save the two files
  and add a -2 suffix to the second one, which would cause the command
  assertion to fail.

blocksatcli/api/test_listen.py

@@ -175,24 +175,24 @@ def test_exec_cmd(self):
     @mock.patch('subprocess.run')
     def test_gossip(self, mock_subproc_run):
         """Test Lightning gossip reception"""
-        filename = 'snapshot.gsp'
+        filename = 'snapshot1.gsp'
         gossip_opts = {'cli': 'historian-cli', 'dest': None}
         self.loopback_test(filename=filename, gossip_opts=gossip_opts)
         expected_cmd = [
             'historian-cli', 'snapshot', 'load',
             os.path.join(self.download_dir, filename)
         ]
-        self.assertTrue(mock_subproc_run.called_with(expected_cmd))
+        mock_subproc_run.assert_called_with(expected_cmd)
 
     @mock.patch('subprocess.run')
     def test_gossip_with_dest(self, mock_subproc_run):
         """Test Lightning gossip reception with a specified destination"""
-        filename = 'snapshot.gsp'
+        filename = 'snapshot2.gsp'
         dest = '127.0.0.1'
         gossip_opts = {'cli': 'historian-cli', 'dest': dest}
         self.loopback_test(filename=filename, gossip_opts=gossip_opts)
         expected_cmd = [
             'historian-cli', 'snapshot', 'load',
             os.path.join(self.download_dir, filename), dest
         ]
-        self.assertTrue(mock_subproc_run.called_with(expected_cmd))
+        mock_subproc_run.assert_called_with(expected_cmd)