diff -r d0f775432705 Lib/_pyio.py
--- a/Lib/_pyio.py	Thu Jun 28 01:45:48 2012 +0200
+++ b/Lib/_pyio.py	Thu Jun 28 12:21:26 2012 +0300
@@ -173,6 +173,8 @@
     if "U" in modes:
         if creating or writing or appending:
             raise ValueError("can't use U and writing mode at once")
+        warnings.warn("Use of 'U' mode is deprecated",
+                      DeprecationWarning)
         reading = True
     if text and binary:
         raise ValueError("can't have text and binary mode at once")
diff -r d0f775432705 Lib/fileinput.py
--- a/Lib/fileinput.py	Thu Jun 28 01:45:48 2012 +0200
+++ b/Lib/fileinput.py	Thu Jun 28 12:21:26 2012 +0300
@@ -224,6 +224,9 @@
         if mode not in ('r', 'rU', 'U', 'rb'):
             raise ValueError("FileInput opening mode must be one of "
                              "'r', 'rU', 'U' and 'rb'")
+        if 'U' in mode:
+            warnings.warn("Use of 'U' mode is deprecated",
+                          DeprecationWarning)
         self._mode = mode
         if openhook:
             if inplace:
diff -r d0f775432705 Lib/imp.py
--- a/Lib/imp.py	Thu Jun 28 01:45:48 2012 +0200
+++ b/Lib/imp.py	Thu Jun 28 12:21:26 2012 +0300
@@ -42,7 +42,7 @@
                   'defined on importlib.machinery instead',
                   DeprecationWarning, 2)
     extensions = [(s, 'rb', C_EXTENSION) for s in extension_suffixes()]
-    source = [(s, 'U', PY_SOURCE) for s in machinery.SOURCE_SUFFIXES]
+    source = [(s, 'r', PY_SOURCE) for s in machinery.SOURCE_SUFFIXES]
     bytecode = [(s, 'rb', PY_COMPILED) for s in machinery.BYTECODE_SUFFIXES]
 
     return extensions + source + bytecode
@@ -228,7 +228,7 @@
         raise ImportError('No module name {!r}'.format(name), name=name)
 
     encoding = None
-    if mode == 'U':
+    if 'b' not in mode:
         with open(file_path, 'rb') as file:
             encoding = tokenize.detect_encoding(file.readline)[0]
     file = open(file_path, mode, encoding=encoding)
diff -r d0f775432705 Lib/zipfile.py
--- a/Lib/zipfile.py	Thu Jun 28 01:45:48 2012 +0200
+++ b/Lib/zipfile.py	Thu Jun 28 12:21:26 2012 +0300
@@ -1098,8 +1098,11 @@
 
     def open(self, name, mode="r", pwd=None):
         """Return file-like object for 'name'."""
+        if 'U' in mode:
+            warnings.warn("Use of 'U' mode is deprecated",
+                          DeprecationWarning)
         if mode not in ("r", "U", "rU"):
-            raise RuntimeError('open() requires mode "r", "U", or "rU"')
+            raise RuntimeError('open() requires mode "r"')
         if pwd and not isinstance(pwd, bytes):
             raise TypeError("pwd: expected bytes, got %s" % type(pwd))
         if not self.fp:
diff -r d0f775432705 Modules/_io/_iomodule.c
--- a/Modules/_io/_iomodule.c	Thu Jun 28 01:45:48 2012 +0200
+++ b/Modules/_io/_iomodule.c	Thu Jun 28 12:21:26 2012 +0300
@@ -310,6 +310,9 @@
                             "can't use U and writing mode at once");
             return NULL;
         }
+        if (PyErr_WarnEx(PyExc_DeprecationWarning,
+                         "Use of 'U' mode is deprecated", 1) < 0)
+            return NULL;
         reading = 1;
     }
 
diff -r d0f775432705 Tools/iobench/iobench.py
--- a/Tools/iobench/iobench.py	Thu Jun 28 01:45:48 2012 +0200
+++ b/Tools/iobench/iobench.py	Thu Jun 28 12:21:26 2012 +0300
@@ -9,6 +9,7 @@
 import re
 import sys
 import time
+import io
 from optparse import OptionParser
 
 out = sys.stdout
@@ -26,6 +27,8 @@
     try:
         return open(fn, mode, encoding=encoding or TEXT_ENCODING)
     except TypeError:
+        if 'r' in mode:
+            mode += 'U'
         return open(fn, mode)
 
 def get_file_sizes():
@@ -382,7 +385,7 @@
             f.write(os.urandom(size))
     # Text files
     chunk = []
-    with text_open(__file__, "rU", encoding='utf8') as f:
+    with text_open(__file__, "r", encoding='utf8') as f:
         for line in f:
             if line.startswith("# <iobench text chunk marker>"):
                 break
diff -r d0f775432705 Tools/scripts/diff.py
--- a/Tools/scripts/diff.py	Thu Jun 28 01:45:48 2012 +0200
+++ b/Tools/scripts/diff.py	Thu Jun 28 12:21:26 2012 +0300
@@ -38,9 +38,9 @@
 
     fromdate = file_mtime(fromfile)
     todate = file_mtime(tofile)
-    with open(fromfile, 'U') as ff:
+    with open(fromfile, 'r') as ff:
         fromlines = ff.readlines()
-    with open(tofile, 'U') as tf:
+    with open(tofile, 'r') as tf:
         tolines = tf.readlines()
 
     if options.u:
diff -r d0f775432705 Tools/scripts/ndiff.py
--- a/Tools/scripts/ndiff.py	Thu Jun 28 01:45:48 2012 +0200
+++ b/Tools/scripts/ndiff.py	Thu Jun 28 12:21:26 2012 +0300
@@ -60,7 +60,7 @@
 # couldn't be opened
 def fopen(fname):
     try:
-        return open(fname, 'U')
+        return open(fname, 'r')
     except IOError as detail:
         return fail("couldn't open " + fname + ": " + str(detail))