Index: Lib/test/test_os.py
===================================================================
--- Lib/test/test_os.py	(revisione 85425)
+++ Lib/test/test_os.py	(copia locale)
@@ -106,7 +106,8 @@
         self.assertFalse(os.path.exists(name),
                     "file already exists for temporary file")
         # make sure we can create the file
-        open(name, "w")
+        with open(name, "w") as _:
+            pass
         self.files.append(name)
 
     def test_tempnam(self):
@@ -163,6 +164,9 @@
                 # dummy file and proceed with the test as normal.
                 fp.close()
                 os.remove(name)
+            finally:
+                if not fp.closed:
+                    fp.close()
 
         fp = os.tmpfile()
         fp.write("foobar")
@@ -199,9 +203,16 @@
             self.check_tempfile(name)
 
     def fdopen_helper(self, *args):
-        fd = os.open(support.TESTFN, os.O_RDONLY)
-        fp2 = os.fdopen(fd, *args)
-        fp2.close()
+        fd = None
+        fp2 = None
+        try:
+            fd = os.open(support.TESTFN, os.O_RDONLY)
+            fp2 = os.fdopen(fd, *args)
+        finally:
+            if fd is not None:
+                fd.close()
+            if fp2 is not None:
+                fp2.close()
 
     def test_fdopen(self):
         self.fdopen_helper()
@@ -213,9 +224,8 @@
     def setUp(self):
         os.mkdir(support.TESTFN)
         self.fname = os.path.join(support.TESTFN, "f1")
-        f = open(self.fname, 'wb')
-        f.write(b"ABC")
-        f.close()
+        with open(self.fname, 'wb') as f:
+            f.write(b"ABC")
 
     def tearDown(self):
         os.unlink(self.fname)
@@ -533,9 +543,8 @@
         os.makedirs(sub2_path)
         os.makedirs(t2_path)
         for path in tmp1_path, tmp2_path, tmp3_path, tmp4_path:
-            f = open(path, "w")
-            f.write("I'm " + path + " and proud of it.  Blame test_os.\n")
-            f.close()
+            with open(path, "w") as f:
+                f.write("I'm " + path + " and proud of it.  Blame test_os.\n")
         if support.can_symlink():
             os.symlink(os.path.abspath(t2_path), link_path)
             sub2_tree = (sub2_path, ["link"], ["tmp3"])
@@ -638,12 +647,10 @@
 
 class DevNullTests(unittest.TestCase):
     def test_devnull(self):
-        f = open(os.devnull, 'w')
-        f.write('hello')
-        f.close()
-        f = open(os.devnull, 'r')
-        self.assertEqual(f.read(), '')
-        f.close()
+        with open(os.devnull, 'w') as f:
+            f.write('hello')
+        with open(os.devnull, 'r') as f:
+            self.assertEqual(f.read(), '')
 
 class URandomTests(unittest.TestCase):
     def test_urandom(self):