Restore _finalizing to not emit a ResourceWarning when closing the file

Author: serhiy-storchaka

Lib/test/test_io/test_fileio.py

@@ -520,6 +520,9 @@ def testFinalizing(self):
         with self.assertRaisesRegex(TypeError,
                                     "can't delete numeric/char attribute"):
             del self.f._finalizing
+        # closing a file which is being finalized emits a ResourceWarning
+        self.f._finalizing = False
+
 
 class PyAutoFileTests(AutoFileTests, unittest.TestCase):
     FileIO = _pyio.FileIO