Issue #16800: tempfile.gettempdir() no longer left temporary files when

the disk is full.  Original patch by Amir Szekely.

Lib/test/test_tempfile.py

@@ -1,6 +1,7 @@
 # tempfile.py unit tests.
 import tempfile
 import errno
+import io
 import os
 import signal
 import sys
@@ -198,7 +199,44 @@ class TestCandidateTempdirList(BaseTestCase):
             # paths in this list.
 
 
-# We test _get_default_tempdir by testing gettempdir.
+# We test _get_default_tempdir some more by testing gettempdir.
+
+class TestGetDefaultTempdir(BaseTestCase):
+    """Test _get_default_tempdir()."""
+
+    def test_no_files_left_behind(self):
+        # use a private empty directory
+        with tempfile.TemporaryDirectory() as our_temp_directory:
+            # force _get_default_tempdir() to consider our empty directory
+            def our_candidate_list():
+                return [our_temp_directory]
+
+            with support.swap_attr(tempfile, "_candidate_tempdir_list",
+                                   our_candidate_list):
+                # verify our directory is empty after _get_default_tempdir()
+                tempfile._get_default_tempdir()
+                self.assertEqual(os.listdir(our_temp_directory), [])
+
+                def raise_OSError(*args, **kwargs):
+                    raise OSError()
+
+                with support.swap_attr(io, "open", raise_OSError):
+                    # test again with failing io.open()
+                    with self.assertRaises(FileNotFoundError):
+                        tempfile._get_default_tempdir()
+                    self.assertEqual(os.listdir(our_temp_directory), [])
+
+                open = io.open
+                def bad_writer(*args, **kwargs):
+                    fp = open(*args, **kwargs)
+                    fp.write = raise_OSError
+                    return fp
+
+                with support.swap_attr(io, "open", bad_writer):
+                    # test again with failing write()
+                    with self.assertRaises(FileNotFoundError):
+                        tempfile._get_default_tempdir()
+                    self.assertEqual(os.listdir(our_temp_directory), [])
 
 
 class TestGetCandidateNames(BaseTestCase):