bpo-37330: open() no longer accept 'U' in file mode (GH-28118)

open(), io.open(), codecs.open() and fileinput.FileInput no longer
accept "U" ("universal newline") in the file mode. This flag was
deprecated since Python 3.3.

1 files changed, 7 insertions, 10 deletions

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 273545a..d52f97b 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -3954,16 +3954,6 @@ class MiscIOTest(unittest.TestCase):
         self.assertEqual(f.mode, "wb")
         f.close()
 
-        with warnings_helper.check_warnings(('', DeprecationWarning)):
-            f = self.open(os_helper.TESTFN, "U", encoding="utf-8")
-        self.assertEqual(f.name,            os_helper.TESTFN)
-        self.assertEqual(f.buffer.name,     os_helper.TESTFN)
-        self.assertEqual(f.buffer.raw.name, os_helper.TESTFN)
-        self.assertEqual(f.mode,            "U")
-        self.assertEqual(f.buffer.mode,     "rb")
-        self.assertEqual(f.buffer.raw.mode, "rb")
-        f.close()
-
         f = self.open(os_helper.TESTFN, "w+", encoding="utf-8")
         self.assertEqual(f.mode,            "w+")
         self.assertEqual(f.buffer.mode,     "rb+") # Does it really matter?
@@ -3977,6 +3967,13 @@ class MiscIOTest(unittest.TestCase):
         f.close()
         g.close()
 
+    def test_removed_u_mode(self):
+        # bpo-37330: The "U" mode has been removed in Python 3.11
+        for mode in ("U", "rU", "r+U"):
+            with self.assertRaises(ValueError) as cm:
+                self.open(os_helper.TESTFN, mode)
+            self.assertIn('invalid mode', str(cm.exception))
+
     def test_open_pipe_with_append(self):
         # bpo-27805: Ignore ESPIPE from lseek() in open().
         r, w = os.pipe()