warnings.catch_warnings() now returns a list or None instead of the custom
WarningsRecorder object. This makes the API simpler to use as no special object
must be learned.

Closes issue 3781.
Review by Benjamin Peterson.
diff --git a/Lib/test/test_py3kwarn.py b/Lib/test/test_py3kwarn.py
index 780de74..aa1ecbb 100644
--- a/Lib/test/test_py3kwarn.py
+++ b/Lib/test/test_py3kwarn.py
@@ -1,7 +1,6 @@
 import unittest
 import sys
-from test.test_support import (catch_warning, CleanImport,
-                               TestSkipped, run_unittest)
+from test.test_support import CleanImport, TestSkipped, run_unittest
 import warnings
 
 from contextlib import nested
@@ -13,11 +12,11 @@
 class TestPy3KWarnings(unittest.TestCase):
 
     def assertWarning(self, _, warning, expected_message):
-        self.assertEqual(str(warning.message), expected_message)
+        self.assertEqual(str(warning[-1].message), expected_message)
 
     def test_backquote(self):
         expected = 'backquote not supported in 3.x; use repr()'
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             exec "`2`" in {}
         self.assertWarning(None, w, expected)
 
@@ -28,71 +27,55 @@
             exec expr in {'f' : f}
 
         expected = "assignment to True or False is forbidden in 3.x"
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             safe_exec("True = False")
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("False = True")
             self.assertWarning(None, w, expected)
-            w.reset()
             try:
                 safe_exec("obj.False = True")
             except NameError: pass
             self.assertWarning(None, w, expected)
-            w.reset()
             try:
                 safe_exec("obj.True = False")
             except NameError: pass
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("def False(): pass")
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("def True(): pass")
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("class False: pass")
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("class True: pass")
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("def f(True=43): pass")
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("def f(False=None): pass")
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("f(False=True)")
             self.assertWarning(None, w, expected)
-            w.reset()
             safe_exec("f(True=1)")
             self.assertWarning(None, w, expected)
 
 
     def test_type_inequality_comparisons(self):
         expected = 'type inequality comparisons not supported in 3.x'
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(int < str, w, expected)
-            w.reset()
             self.assertWarning(type < object, w, expected)
 
     def test_object_inequality_comparisons(self):
         expected = 'comparing unequal types not supported in 3.x'
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(str < [], w, expected)
-            w.reset()
             self.assertWarning(object() < (1, 2), w, expected)
 
     def test_dict_inequality_comparisons(self):
         expected = 'dict inequality comparisons not supported in 3.x'
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning({} < {2:3}, w, expected)
-            w.reset()
             self.assertWarning({} <= {}, w, expected)
-            w.reset()
             self.assertWarning({} > {2:3}, w, expected)
-            w.reset()
             self.assertWarning({2:3} >= {}, w, expected)
 
     def test_cell_inequality_comparisons(self):
@@ -103,9 +86,8 @@
             return g
         cell0, = f(0).func_closure
         cell1, = f(1).func_closure
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(cell0 == cell1, w, expected)
-            w.reset()
             self.assertWarning(cell0 < cell1, w, expected)
 
     def test_code_inequality_comparisons(self):
@@ -114,13 +96,10 @@
             pass
         def g(x):
             pass
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(f.func_code < g.func_code, w, expected)
-            w.reset()
             self.assertWarning(f.func_code <= g.func_code, w, expected)
-            w.reset()
             self.assertWarning(f.func_code >= g.func_code, w, expected)
-            w.reset()
             self.assertWarning(f.func_code > g.func_code, w, expected)
 
     def test_builtin_function_or_method_comparisons(self):
@@ -128,13 +107,10 @@
                     'inequality comparisons not supported in 3.x')
         func = eval
         meth = {}.get
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(func < meth, w, expected)
-            w.reset()
             self.assertWarning(func > meth, w, expected)
-            w.reset()
             self.assertWarning(meth <= func, w, expected)
-            w.reset()
             self.assertWarning(meth >= func, w, expected)
 
     def test_sort_cmp_arg(self):
@@ -142,18 +118,15 @@
         lst = range(5)
         cmp = lambda x,y: -1
 
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(lst.sort(cmp=cmp), w, expected)
-            w.reset()
             self.assertWarning(sorted(lst, cmp=cmp), w, expected)
-            w.reset()
             self.assertWarning(lst.sort(cmp), w, expected)
-            w.reset()
             self.assertWarning(sorted(lst, cmp), w, expected)
 
     def test_sys_exc_clear(self):
         expected = 'sys.exc_clear() not supported in 3.x; use except clauses'
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(sys.exc_clear(), w, expected)
 
     def test_methods_members(self):
@@ -162,17 +135,17 @@
             __methods__ = ['a']
             __members__ = ['b']
         c = C()
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(dir(c), w, expected)
 
     def test_softspace(self):
         expected = 'file.softspace not supported in 3.x'
         with file(__file__) as f:
-            with catch_warning() as w:
+            with warnings.catch_warnings(record=True) as w:
                 self.assertWarning(f.softspace, w, expected)
             def set():
                 f.softspace = 0
-            with catch_warning() as w:
+            with warnings.catch_warnings(record=True) as w:
                 self.assertWarning(set(), w, expected)
 
     def test_slice_methods(self):
@@ -188,60 +161,59 @@
         expected = "in 3.x, __{0}slice__ has been removed; use __{0}item__"
 
         for obj in (Spam(), Egg()):
-            with catch_warning() as w:
+            with warnings.catch_warnings(record=True) as w:
                 self.assertWarning(obj[1:2], w, expected.format('get'))
-                w.reset()
                 del obj[3:4]
                 self.assertWarning(None, w, expected.format('del'))
-                w.reset()
                 obj[4:5] = "eggs"
                 self.assertWarning(None, w, expected.format('set'))
 
     def test_tuple_parameter_unpacking(self):
         expected = "tuple parameter unpacking has been removed in 3.x"
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             exec "def f((a, b)): pass"
             self.assertWarning(None, w, expected)
 
     def test_buffer(self):
         expected = 'buffer() not supported in 3.x'
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             self.assertWarning(buffer('a'), w, expected)
 
     def test_file_xreadlines(self):
         expected = ("f.xreadlines() not supported in 3.x, "
                     "try 'for line in f' instead")
         with file(__file__) as f:
-            with catch_warning() as w:
+            with warnings.catch_warnings(record=True) as w:
                 self.assertWarning(f.xreadlines(), w, expected)
 
     def test_hash_inheritance(self):
-        with catch_warning() as w:
+        with warnings.catch_warnings(record=True) as w:
             # With object as the base class
             class WarnOnlyCmp(object):
                 def __cmp__(self, other): pass
             self.assertEqual(len(w), 1)
             self.assertWarning(None, w,
                  "Overriding __cmp__ blocks inheritance of __hash__ in 3.x")
-            w.reset()
+            del w[:]
             class WarnOnlyEq(object):
                 def __eq__(self, other): pass
             self.assertEqual(len(w), 1)
             self.assertWarning(None, w,
                  "Overriding __eq__ blocks inheritance of __hash__ in 3.x")
-            w.reset()
+            del w[:]
             class WarnCmpAndEq(object):
                 def __cmp__(self, other): pass
                 def __eq__(self, other): pass
             self.assertEqual(len(w), 2)
-            self.assertWarning(None, w[-2],
+            self.assertWarning(None, w[:1],
                  "Overriding __cmp__ blocks inheritance of __hash__ in 3.x")
             self.assertWarning(None, w,
                  "Overriding __eq__ blocks inheritance of __hash__ in 3.x")
-            w.reset()
+            del w[:]
             class NoWarningOnlyHash(object):
                 def __hash__(self): pass
             self.assertEqual(len(w), 0)
+            del w[:]
             # With an intermediate class in the heirarchy
             class DefinesAllThree(object):
                 def __cmp__(self, other): pass
@@ -252,22 +224,22 @@
             self.assertEqual(len(w), 1)
             self.assertWarning(None, w,
                  "Overriding __cmp__ blocks inheritance of __hash__ in 3.x")
-            w.reset()
+            del w[:]
             class WarnOnlyEq(DefinesAllThree):
                 def __eq__(self, other): pass
             self.assertEqual(len(w), 1)
             self.assertWarning(None, w,
                  "Overriding __eq__ blocks inheritance of __hash__ in 3.x")
-            w.reset()
+            del w[:]
             class WarnCmpAndEq(DefinesAllThree):
                 def __cmp__(self, other): pass
                 def __eq__(self, other): pass
             self.assertEqual(len(w), 2)
-            self.assertWarning(None, w[-2],
+            self.assertWarning(None, w[:1],
                  "Overriding __cmp__ blocks inheritance of __hash__ in 3.x")
             self.assertWarning(None, w,
                  "Overriding __eq__ blocks inheritance of __hash__ in 3.x")
-            w.reset()
+            del w[:]
             class NoWarningOnlyHash(DefinesAllThree):
                 def __hash__(self): pass
             self.assertEqual(len(w), 0)
@@ -310,7 +282,7 @@
     def check_removal(self, module_name, optional=False):
         """Make sure the specified module, when imported, raises a
         DeprecationWarning and specifies itself in the message."""
-        with nested(CleanImport(module_name), catch_warning(record=False)):
+        with nested(CleanImport(module_name), warnings.catch_warnings()):
             warnings.filterwarnings("error", ".+ removed",
                                     DeprecationWarning, __name__)
             try:
@@ -348,36 +320,36 @@
         def dumbo(where, names, args): pass
         for path_mod in ("ntpath", "macpath", "os2emxpath", "posixpath"):
             mod = __import__(path_mod)
-            with catch_warning() as w:
+            with warnings.catch_warnings(record=True) as w:
                 mod.walk("crashers", dumbo, None)
-            self.assertEquals(str(w.message), msg)
+            self.assertEquals(str(w[-1].message), msg)
 
     def test_commands_members(self):
         import commands
         members = {"mk2arg" : 2, "mkarg" : 1, "getstatus" : 1}
         for name, arg_count in members.items():
-            with catch_warning(record=False):
+            with warnings.catch_warnings():
                 warnings.filterwarnings("error")
                 func = getattr(commands, name)
                 self.assertRaises(DeprecationWarning, func, *([None]*arg_count))
 
     def test_reduce_move(self):
         from operator import add
-        with catch_warning(record=False):
+        with warnings.catch_warnings():
             warnings.filterwarnings("error", "reduce")
             self.assertRaises(DeprecationWarning, reduce, add, range(10))
 
     def test_mutablestring_removal(self):
         # UserString.MutableString has been removed in 3.0.
         import UserString
-        with catch_warning(record=False):
+        with warnings.catch_warnings():
             warnings.filterwarnings("error", ".*MutableString",
                                     DeprecationWarning)
             self.assertRaises(DeprecationWarning, UserString.MutableString)
 
 
 def test_main():
-    with catch_warning():
+    with warnings.catch_warnings():
         warnings.simplefilter("always")
         run_unittest(TestPy3KWarnings,
                      TestStdlibRemovals)