diff --git a/Lib/string.py b/Lib/string.py
index 5e13d15..9c0ebe1 100644
--- a/Lib/string.py
+++ b/Lib/string.py
@@ -607,7 +607,7 @@
             return str(value)
         elif conversion is None:
             return value
-        raise ValueError("Unknown converion specifier {0!s}".format(conversion))
+        raise ValueError("Unknown conversion specifier {0!s}".format(conversion))
 
 
     # returns an iterable that contains tuples of the form:
diff --git a/Lib/test/string_tests.py b/Lib/test/string_tests.py
index 7cfe65b..56cbc35 100644
--- a/Lib/test/string_tests.py
+++ b/Lib/test/string_tests.py
@@ -1119,7 +1119,7 @@
             format = '%%.%if' % prec
             value = 0.01
             for x in xrange(60):
-                value = value * 3.141592655 / 3.0 * 10.0
+                value = value * 3.14159265359 / 3.0 * 10.0
                 self.checkcall(format, "__mod__", value)
 
     def test_inplace_rewrites(self):
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 516d6d9..d0f5662 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -9,14 +9,28 @@
 import re
 import sys
 import copy
+import functools
 import pickle
 import tempfile
 import unittest
-import warnings
 import test.test_support
 import test.string_tests
 import test.buffer_tests
 
+
+if sys.flags.bytes_warning:
+    def check_bytes_warnings(func):
+        @functools.wraps(func)
+        def wrapper(*args, **kw):
+            with test.test_support.check_warnings(('', BytesWarning)):
+                return func(*args, **kw)
+        return wrapper
+else:
+    # no-op
+    def check_bytes_warnings(func):
+        return func
+
+
 class Indexable:
     def __init__(self, value=0):
         self.value = value
@@ -26,12 +40,6 @@
 
 class BaseBytesTest(unittest.TestCase):
 
-    def setUp(self):
-        self.warning_filters = warnings.filters[:]
-
-    def tearDown(self):
-        warnings.filters = self.warning_filters
-
     def test_basics(self):
         b = self.type2test()
         self.assertEqual(type(b), self.type2test)
@@ -120,8 +128,8 @@
         self.assertFalse(b3 <  b2)
         self.assertFalse(b3 <= b2)
 
+    @check_bytes_warnings
     def test_compare_to_str(self):
-        warnings.simplefilter('ignore', BytesWarning)
         # Byte comparisons with unicode should always fail!
         # Test this for all expected byte orders and Unicode character sizes
         self.assertEqual(self.type2test(b"\0a\0b\0c") == u"abc", False)
@@ -795,14 +803,8 @@
     # Test various combinations of bytes and bytearray
     #
 
-    def setUp(self):
-        self.warning_filters = warnings.filters[:]
-
-    def tearDown(self):
-        warnings.filters = self.warning_filters
-
+    @check_bytes_warnings
     def test_repr_str(self):
-        warnings.simplefilter('ignore', BytesWarning)
         for f in str, repr:
             self.assertEqual(f(bytearray()), "bytearray(b'')")
             self.assertEqual(f(bytearray([0])), "bytearray(b'\\x00')")
@@ -853,8 +855,8 @@
         b = bytearray(buf)
         self.assertEqual(b, bytearray(sample))
 
+    @check_bytes_warnings
     def test_to_str(self):
-        warnings.simplefilter('ignore', BytesWarning)
         self.assertEqual(str(b''), "b''")
         self.assertEqual(str(b'x'), "b'x'")
         self.assertEqual(str(b'\x80'), "b'\\x80'")
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 1151e86..b309704 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -593,9 +593,9 @@
         )
 
         # UTF-8 specific decoding tests
-        self.assertEqual(unicode('\xf0\xa3\x91\x96', 'utf-8'), u'\U00023456' )
-        self.assertEqual(unicode('\xf0\x90\x80\x82', 'utf-8'), u'\U00010002' )
-        self.assertEqual(unicode('\xe2\x82\xac', 'utf-8'), u'\u20ac' )
+        self.assertEqual(unicode('\xf0\xa3\x91\x96', 'utf-8'), u'\U00023456')
+        self.assertEqual(unicode('\xf0\x90\x80\x82', 'utf-8'), u'\U00010002')
+        self.assertEqual(unicode('\xe2\x82\xac', 'utf-8'), u'\u20ac')
 
         # Other possible utf-8 test cases:
         # * strict decoding testing for all of the
@@ -1360,8 +1360,8 @@
             def __unicode__(self):
                 return u'__unicode__ overridden'
         u = U(u'xxx')
-        self.assertEquals("%s" % u, u'__unicode__ overridden')
-        self.assertEquals("{}".format(u), u'__unicode__ overridden')
+        self.assertEqual("%s" % u, u'__unicode__ overridden')
+        self.assertEqual("{}".format(u), u'__unicode__ overridden')
 
 
 def test_main():