UserString.MutableString has been removed in Python 3.0.

Works on issue #2877. Thanks Quentin Gallet-Gilles for the patch.

Doc/library/userdict.rst

@@ -178,6 +178,9 @@ The :mod:`UserString` module defines the following classes:
    mutable object as dictionary key, which would be otherwise very error prone and
    hard to track down.
 
+   .. deprecated:: 2.6
+      The :class:`MutableString` class has been removed in Python 3.0.
+
 In addition to supporting the methods and operations of string and Unicode
 objects (see section :ref:`string-methods`), :class:`UserString` instances
 provide the following attribute:

Lib/UserString.py

@@ -146,6 +146,9 @@ class MutableString(UserString, collections.MutableSequence):
 
     A faster and better solution is to rewrite your program using lists."""
     def __init__(self, string=""):
+        from warnings import warnpy3k
+        warnpy3k('the class UserString.MutableString has been removed in '
+                    'Python 3.0', stacklevel=2)
         self.data = string
     def __hash__(self):
         raise TypeError, "unhashable type (it is mutable)"

Lib/test/test_py3kwarn.py

@@ -219,6 +219,14 @@ class TestStdlibRemovals(unittest.TestCase):
                 func = getattr(commands, name)
                 self.assertRaises(DeprecationWarning, func, *([None]*arg_count))
 
+    def test_mutablestring_removal(self):
+        # UserString.MutableString has been removed in 3.0.
+        import UserString
+        with catch_warning(record=False):
+            warnings.filterwarnings("error", ".*MutableString",
+                                    DeprecationWarning)
+            self.assertRaises(DeprecationWarning, UserString.MutableString)
+
 
 def test_main():
     with catch_warning(record=True):

Lib/test/test_userstring.py

@@ -4,8 +4,8 @@
 
 import string
 from test import test_support, string_tests
-
 from UserString import UserString, MutableString
+import warnings
 
 class UserStringTest(
     string_tests.CommonTest,
@@ -135,7 +135,10 @@ class MutableStringTest(UserStringTest):
         self.assertEqual(s, "")
 
 def test_main():
-    test_support.run_unittest(UserStringTest, MutableStringTest)
+    with test_support.catch_warning(record=False):
+        warnings.filterwarnings("ignore", ".*MutableString",
+                                DeprecationWarning)
+        test_support.run_unittest(UserStringTest, MutableStringTest)
 
 if __name__ == "__main__":
     test_main()

Misc/NEWS

@@ -63,6 +63,9 @@ Extension Modules
 Library
 -------
 
+Issue #2877 - The UserString.MutableString class has been removed in
+			  Python 3.0.
+
 - Do not close external file objects passed to tarfile.open(mode='w:bz2')
   when the TarFile is closed.