Add warning for base64 encode functions

.gitignore

@@ -15,6 +15,7 @@
 *.profclang?
 *.profraw
 *.dyn
+.history/
 Doc/build/
 Doc/venv/
 Doc/.venv/

Lib/base64.py

@@ -9,7 +9,8 @@
 import struct
 import string
 import binascii
-from warnings import warnpy3k_with_fix
+from warnings import warnpy3k_with_fix, warnpy3k
+from functools import wraps
 
 
 __all__ = [
@@ -367,5 +368,20 @@ def test1():
     print s0, repr(s1), s2
 
 
+def _warn_encode(func, name):
+    @wraps(func)
+    def encode_wrapper(*args, **kwargs):
+        warnpy3k(
+            "base64.{0} returns str in Python 2 (bytes in 3.x)".format(name),
+            UserWarning,
+            stacklevel= 2,
+            )
+        return func(*args, **kwargs)
+    return encode_wrapper
+
+
+for _name in ["b64encode", "b32encode", "b16encode"]:
+    globals()[_name] = _warn_encode(globals()[_name], _name)
+
 if __name__ == '__main__':
     test()

Lib/test/test_py3kwarn.py

@@ -2,6 +2,7 @@
 import sys
 from test.test_support import check_py3k_warnings, CleanImport, run_unittest
 import warnings
+import base64
 from test import test_support
 
 if not sys.py3kwarning:
@@ -384,7 +385,22 @@ def test_raise_three_components(self):
                     use 'raise' with a single object"""
         with check_py3k_warnings() as w:
             excType, excValue, excTraceback = sys.exc_info()
-
+
+    def test_b64encode_warns(self):
+        expected = "base64.b64encode returns str in Python 2 (bytes in 3.x)"
+        base64.b64encode(b'test')
+        check_py3k_warnings(expected, UserWarning)
+
+    def test_b32encode_warns(self):
+        expected = "base64.b32encode returns str in Python 2 (bytes in 3.x)"
+        base64.b32encode(b'test')
+        check_py3k_warnings(expected, UserWarning)
+
+    def test_b16encode_warns(self):
+        expected = "base64.b16encode returns str in Python 2 (bytes in 3.x)"
+        base64.b16encode(b'test')
+        check_py3k_warnings(expected, UserWarning)
+
 
 class TestStdlibRemovals(unittest.TestCase):