Fix ResourceWarning in test_unittest when interrupted

Lib/unittest/test/test_runner.py

@@ -290,6 +290,7 @@ class Test_TextTestRunner(unittest.TestCase):
 
         # no args -> all the warnings are printed, unittest warnings only once
         p = subprocess.Popen([sys.executable, '_test_warnings.py'], **opts)
+        with p:
             out, err = get_parse_out_err(p)
         self.assertIn(b'OK', err)
         # check that the total number of warnings in the output is correct
@@ -311,6 +312,7 @@ class Test_TextTestRunner(unittest.TestCase):
         # in all these cases no warnings are printed
         for args in args_list:
             p = subprocess.Popen(args, **opts)
+            with p:
                 out, err = get_parse_out_err(p)
             self.assertIn(b'OK', err)
             self.assertEqual(len(out), 0)
@@ -320,6 +322,7 @@ class Test_TextTestRunner(unittest.TestCase):
         #                                     unittest warnings only once
         p = subprocess.Popen([sys.executable, '_test_warnings.py', 'always'],
                              **opts)
+        with p:
             out, err = get_parse_out_err(p)
         self.assertIn(b'OK', err)
         self.assertEqual(len(out), 14)