fix test

Author: kumaraditya303

Lib/test/test_asyncio/test_subprocess.py

@@ -233,6 +233,7 @@ def test_kill_issue43884(self):
             # expect 1 but sometimes get 0
         else:
             self.assertEqual(-signal.SIGKILL, returncode)
+        self.loop.run_until_complete(proc.stdout.read())
 
     def test_terminate(self):
         args = PROGRAM_BLOCKED