ci: do not count unreaped zombies as live processes in the guard tests [CI]

The CI container has no init to reap killed processes, so kill(pid, 0) still succeeded for a process the guard had already killed.

scripts/test-guard-step.py

@@ -13,6 +13,19 @@ ROOT = Path(__file__).resolve().parents[1]
 GUARD = ROOT / 'ci/guard-step.py'
 
 
+def alive(pid):
+    """进程还在运行。已经被杀但没人回收的僵尸进程（CI 容器里没有 init）不算。"""
+    try:
+        os.kill(pid, 0)
+    except ProcessLookupError:
+        return False
+    try:
+        state = Path(f'/proc/{pid}/stat').read_text().rsplit(')', 1)[1].split()[0]
+    except (OSError, IndexError):
+        return True
+    return state != 'Z'
+
+
 class GuardStepTests(unittest.TestCase):
     def setUp(self):
         self.directory = tempfile.TemporaryDirectory()
@@ -57,8 +70,7 @@ class GuardStepTests(unittest.TestCase):
         step.send_signal(signal.SIGTERM)
         self.assertEqual(step.wait(timeout=30), 128 + signal.SIGTERM)
         time.sleep(0.5)
-        with self.assertRaises(ProcessLookupError):
-            os.kill(child, 0)
+        self.assertFalse(alive(child))
         self.assertEqual(self.guard('next', 30, 'true', stderr=subprocess.DEVNULL).wait(timeout=20), 125)
 
     def test_a_background_process_left_by_a_finished_step_is_killed(self):
@@ -66,8 +78,7 @@ class GuardStepTests(unittest.TestCase):
         step = self.guard('leaky', 30, 'bash', '-c', f'sleep 120 & echo $! > {pid_file}', stderr=subprocess.DEVNULL)
         self.assertEqual(step.wait(timeout=20), 0)
         time.sleep(0.5)
-        with self.assertRaises(ProcessLookupError):
-            os.kill(int(pid_file.read_text()), 0)
+        self.assertFalse(alive(int(pid_file.read_text())))
 
     def test_the_pipeline_deadline_is_the_last_resort(self):
         self.env['MOSHIRO_PIPELINE_DEADLINE'] = '2'