bpo-37330: open() no longer accept 'U' in file mode (GH-16959)

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 1fe1cba..ad22dfe 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -3886,16 +3886,6 @@ class MiscIOTest(unittest.TestCase):
         self.assertEqual(f.mode, "wb")
         f.close()
 
-        with support.check_warnings(('', DeprecationWarning)):
-            f = self.open(support.TESTFN, "U")
-        self.assertEqual(f.name,            support.TESTFN)
-        self.assertEqual(f.buffer.name,     support.TESTFN)
-        self.assertEqual(f.buffer.raw.name, support.TESTFN)
-        self.assertEqual(f.mode,            "U")
-        self.assertEqual(f.buffer.mode,     "rb")
-        self.assertEqual(f.buffer.raw.mode, "rb")
-        f.close()
-
         f = self.open(support.TESTFN, "w+")
         self.assertEqual(f.mode,            "w+")
         self.assertEqual(f.buffer.mode,     "rb+") # Does it really matter?
@@ -3909,6 +3899,13 @@ class MiscIOTest(unittest.TestCase):
         f.close()
         g.close()
 
+    def test_removed_u_mode(self):
+        # "U" mode has been removed in Python 3.9
+        for mode in ("U", "rU", "r+U"):
+            with self.assertRaises(ValueError) as cm:
+                self.open(support.TESTFN, mode)
+            self.assertIn('invalid mode', str(cm.exception))
+
     def test_io_after_close(self):
         for kwargs in [
                 {"mode": "w"},