Improve TUN routing readability

Signed-off-by: Loren Eteval <loren.eteval@proton.me>

tests/test_sing_tun_linux_host.py

@@ -85,6 +85,7 @@ class SingTUNLinuxHostTest(unittest.TestCase):
                 Path(arguments[2]).name.startswith(tempfile.gettempprefix())
             )
             self.assertEqual(Path(arguments[2]).suffix, '.sh')
+
             scripts.append(Path(arguments[2]).read_text(encoding='utf-8'))
             return process
 
@@ -103,6 +104,7 @@ class SingTUNLinuxHostTest(unittest.TestCase):
             self.host.applyDNS('1.1.1.1')
 
         self.assertEqual(self.host.index, 77)
+
         self.assertIn('ip tuntap add dev utun101 mode tun user 1000', scripts[0])
         self.assertIn('ip link set dev utun101 mtu 1500', scripts[0])
         self.assertIn('ip -6 addr add fd00::1/64 dev utun101', scripts[0])
@@ -142,6 +144,7 @@ class SingTUNLinuxHostTest(unittest.TestCase):
                 )
 
         directory = Path(self.host._directory.name)
+
         self.assertIs(self.host._process, process)
         self.assertEqual(len(list(directory.glob('*.sh'))), 1)
         self.assertTrue((directory / 'cancelled').exists())
@@ -180,8 +183,10 @@ class SingTUNLinuxHostTest(unittest.TestCase):
                 root = Path(directory).resolve()
                 net = root / 'net'
                 binDirectory = root / 'bin'
+
                 net.mkdir()
                 binDirectory.mkdir()
+
                 ip = binDirectory / 'ip'
 
                 # This fixture only creates/removes files under its temporary
@@ -217,6 +222,7 @@ class SingTUNLinuxHostTest(unittest.TestCase):
 
                 def launch(arguments, **kwargs):
                     self.assertEqual(arguments[:2], ['pkexec', 'bash'])
+
                     script = Path(arguments[-1])
                     text = script.read_text(encoding='utf-8')
                     text = text.replace('/sys/class/net', net.as_posix())
@@ -239,6 +245,7 @@ class SingTUNLinuxHostTest(unittest.TestCase):
                         FAKE_CANCEL=(script.parent / 'cancelled').as_posix(),
                         FAKE_SCRIPT=script.as_posix(),
                     )
+
                     return realPopen([bash, str(script)], env=environment, **kwargs)
 
                 with mock.patch.object(
@@ -254,6 +261,7 @@ class SingTUNLinuxHostTest(unittest.TestCase):
                 ):
                     if failure == 'none':
                         self.host.prepare()
+
                         self.assertEqual(self.host.index, 77)
                     else:
                         with self.assertRaisesRegex(