Index: Lib/tokenize.py
===================================================================
--- Lib/tokenize.py	(revision 58930)
+++ Lib/tokenize.py	(working copy)
@@ -69,10 +69,10 @@
 Single3 = r"[^'\\]*(?:(?:\\.|'(?!''))[^'\\]*)*'''"
 # Tail end of """ string.
 Double3 = r'[^"\\]*(?:(?:\\.|"(?!""))[^"\\]*)*"""'
-Triple = group("[uU]?[rR]?'''", '[uU]?[rR]?"""')
+Triple = group("[bB]?[rR]?'''", '[bB]?[rR]?"""')
 # Single-line ' or " string.
-String = group(r"[uU]?[rR]?'[^\n'\\]*(?:\\.[^\n'\\]*)*'",
-               r'[uU]?[rR]?"[^\n"\\]*(?:\\.[^\n"\\]*)*"')
+String = group(r"[bB]?[rR]?'[^\n'\\]*(?:\\.[^\n'\\]*)*'",
+               r'[bB]?[rR]?"[^\n"\\]*(?:\\.[^\n"\\]*)*"')
 
 # Because of leftmost-then-longest match semantics, be sure to put the
 # longest operators first (e.g., if = came before ==, == would get
@@ -90,9 +90,9 @@
 Token = Ignore + PlainToken
 
 # First (or only) line of ' or " string.
-ContStr = group(r"[uU]?[rR]?'[^\n'\\]*(?:\\.[^\n'\\]*)*" +
+ContStr = group(r"[bB]?[rR]?'[^\n'\\]*(?:\\.[^\n'\\]*)*" +
                 group("'", r'\\\r?\n'),
-                r'[uU]?[rR]?"[^\n"\\]*(?:\\.[^\n"\\]*)*' +
+                r'[bB]?[rR]?"[^\n"\\]*(?:\\.[^\n"\\]*)*' +
                 group('"', r'\\\r?\n'))
 PseudoExtras = group(r'\\\r?\n', Comment, Triple)
 PseudoToken = Whitespace + group(PseudoExtras, Number, Funny, ContStr, Name)
@@ -102,28 +102,28 @@
 endprogs = {"'": re.compile(Single), '"': re.compile(Double),
             "'''": single3prog, '"""': double3prog,
             "r'''": single3prog, 'r"""': double3prog,
-            "u'''": single3prog, 'u"""': double3prog,
-            "ur'''": single3prog, 'ur"""': double3prog,
+            "b'''": single3prog, 'b"""': double3prog,
+            "br'''": single3prog, 'br"""': double3prog,
             "R'''": single3prog, 'R"""': double3prog,
-            "U'''": single3prog, 'U"""': double3prog,
-            "uR'''": single3prog, 'uR"""': double3prog,
-            "Ur'''": single3prog, 'Ur"""': double3prog,
-            "UR'''": single3prog, 'UR"""': double3prog,
-            'r': None, 'R': None, 'u': None, 'U': None}
+            "B'''": single3prog, 'B"""': double3prog,
+            "bR'''": single3prog, 'bR"""': double3prog,
+            "Br'''": single3prog, 'Br"""': double3prog,
+            "BR'''": single3prog, 'BR"""': double3prog,
+            'r': None, 'R': None, 'b': None, 'B': None}
 
 triple_quoted = {}
 for t in ("'''", '"""',
           "r'''", 'r"""', "R'''", 'R"""',
-          "u'''", 'u"""', "U'''", 'U"""',
-          "ur'''", 'ur"""', "Ur'''", 'Ur"""',
-          "uR'''", 'uR"""', "UR'''", 'UR"""'):
+          "b'''", 'b"""', "B'''", 'B"""',
+          "br'''", 'br"""', "Br'''", 'Br"""',
+          "bR'''", 'bR"""', "BR'''", 'BR"""'):
     triple_quoted[t] = t
 single_quoted = {}
 for t in ("'", '"',
           "r'", 'r"', "R'", 'R"',
-          "u'", 'u"', "U'", 'U"',
-          "ur'", 'ur"', "Ur'", 'Ur"',
-          "uR'", 'uR"', "UR'", 'UR"' ):
+          "b'", 'b"', "B'", 'B"',
+          "br'", 'br"', "Br'", 'Br"',
+          "bR'", 'bR"', "BR'", 'BR"' ):
     single_quoted[t] = t
 
 tabsize = 8
Index: Lib/test/test_tokenize.py
===================================================================
--- Lib/test/test_tokenize.py	(revision 58930)
+++ Lib/test/test_tokenize.py	(working copy)
@@ -183,17 +183,26 @@
 
     next_time = time.time() + _PRINT_WORKING_MSG_INTERVAL
 
+    # Validate the tokenize_tests.txt file.
+    # This makes sure it's compiles and displays any errors in it.
+    f = open(findfile('tokenize_tests.txt'))
+    sf = f.read()
+    f.close()
+    cf = compile(sf, 'tokenize_tests.txt', 'exec')
+    
     # This displays the tokenization of tokenize_tests.py to stdout, and
     # regrtest.py checks that this equals the expected output (in the
     # test/output/ directory).
     f = open(findfile('tokenize_tests.txt'))
     tokenize(f.readline)
     f.close()
-
-    # Now run test_roundtrip() over tokenize_test.py too, and over all
+   
+    # Now run test_roundtrip() over test_tokenize.py too, and over all
     # (if the "compiler" resource is enabled) or a small random sample (if
     # "compiler" is not enabled) of the test*.py files.
-    f = findfile('tokenize_tests.txt')
+    f = findfile('test_tokenize.py')
+    if verbose:
+        print('    round trip: ', f, file=sys.__stdout__)
     test_roundtrip(f)
 
     testdir = os.path.dirname(f) or os.curdir
Index: Lib/test/tokenize_tests.txt
===================================================================
--- Lib/test/tokenize_tests.txt	(revision 58930)
+++ Lib/test/tokenize_tests.txt	(working copy)
@@ -110,19 +110,19 @@
 bar \\ baz
 """ + R'''spam
 '''
-x = u'abc' + U'ABC'
-y = u"abc" + U"ABC"
-x = ur'abc' + Ur'ABC' + uR'ABC' + UR'ABC'
-y = ur"abc" + Ur"ABC" + uR"ABC" + UR"ABC"
-x = ur'\\' + UR'\\'
-x = ur'\'' + ''
-y = ur'''
+x = b'abc' + B'ABC'
+y = b"abc" + B"ABC"
+x = br'abc' + Br'ABC' + bR'ABC' + BR'ABC'
+y = br"abc" + Br"ABC" + bR"ABC" + BR"ABC"
+x = br'\\' + BR'\\'
+x = br'\'' + ''
+y = br'''
 foo bar \\
-baz''' + UR'''
+baz''' + BR'''
 foo'''
-y = Ur"""foo
+y = Br"""foo
 bar \\ baz
-""" + uR'''spam
+""" + bR'''spam
 '''
 
 # Indentation
Index: Lib/test/output/test_tokenize
===================================================================
--- Lib/test/output/test_tokenize	(revision 58930)
+++ Lib/test/output/test_tokenize	(working copy)
@@ -342,59 +342,59 @@
 112,3-112,4:	NEWLINE	'\n'
 113,0-113,1:	NAME	'x'
 113,2-113,3:	OP	'='
-113,4-113,10:	STRING	"u'abc'"
+113,4-113,10:	STRING	"b'abc'"
 113,11-113,12:	OP	'+'
-113,13-113,19:	STRING	"U'ABC'"
+113,13-113,19:	STRING	"B'ABC'"
 113,19-113,20:	NEWLINE	'\n'
 114,0-114,1:	NAME	'y'
 114,2-114,3:	OP	'='
-114,4-114,10:	STRING	'u"abc"'
+114,4-114,10:	STRING	'b"abc"'
 114,11-114,12:	OP	'+'
-114,13-114,19:	STRING	'U"ABC"'
+114,13-114,19:	STRING	'B"ABC"'
 114,19-114,20:	NEWLINE	'\n'
 115,0-115,1:	NAME	'x'
 115,2-115,3:	OP	'='
-115,4-115,11:	STRING	"ur'abc'"
+115,4-115,11:	STRING	"br'abc'"
 115,12-115,13:	OP	'+'
-115,14-115,21:	STRING	"Ur'ABC'"
+115,14-115,21:	STRING	"Br'ABC'"
 115,22-115,23:	OP	'+'
-115,24-115,31:	STRING	"uR'ABC'"
+115,24-115,31:	STRING	"bR'ABC'"
 115,32-115,33:	OP	'+'
-115,34-115,41:	STRING	"UR'ABC'"
+115,34-115,41:	STRING	"BR'ABC'"
 115,41-115,42:	NEWLINE	'\n'
 116,0-116,1:	NAME	'y'
 116,2-116,3:	OP	'='
-116,4-116,11:	STRING	'ur"abc"'
+116,4-116,11:	STRING	'br"abc"'
 116,12-116,13:	OP	'+'
-116,14-116,21:	STRING	'Ur"ABC"'
+116,14-116,21:	STRING	'Br"ABC"'
 116,22-116,23:	OP	'+'
-116,24-116,31:	STRING	'uR"ABC"'
+116,24-116,31:	STRING	'bR"ABC"'
 116,32-116,33:	OP	'+'
-116,34-116,41:	STRING	'UR"ABC"'
+116,34-116,41:	STRING	'BR"ABC"'
 116,41-116,42:	NEWLINE	'\n'
 117,0-117,1:	NAME	'x'
 117,2-117,3:	OP	'='
-117,4-117,10:	STRING	"ur'\\\\'"
+117,4-117,10:	STRING	"br'\\\\'"
 117,11-117,12:	OP	'+'
-117,13-117,19:	STRING	"UR'\\\\'"
+117,13-117,19:	STRING	"BR'\\\\'"
 117,19-117,20:	NEWLINE	'\n'
 118,0-118,1:	NAME	'x'
 118,2-118,3:	OP	'='
-118,4-118,10:	STRING	"ur'\\''"
+118,4-118,10:	STRING	"br'\\''"
 118,11-118,12:	OP	'+'
 118,13-118,15:	STRING	"''"
 118,15-118,16:	NEWLINE	'\n'
 119,0-119,1:	NAME	'y'
 119,2-119,3:	OP	'='
-119,4-121,6:	STRING	"ur'''\nfoo bar \\\\\nbaz'''"
+119,4-121,6:	STRING	"br'''\nfoo bar \\\\\nbaz'''"
 121,7-121,8:	OP	'+'
-121,9-122,6:	STRING	"UR'''\nfoo'''"
+121,9-122,6:	STRING	"BR'''\nfoo'''"
 122,6-122,7:	NEWLINE	'\n'
 123,0-123,1:	NAME	'y'
 123,2-123,3:	OP	'='
-123,4-125,3:	STRING	'Ur"""foo\nbar \\\\ baz\n"""'
+123,4-125,3:	STRING	'Br"""foo\nbar \\\\ baz\n"""'
 125,4-125,5:	OP	'+'
-125,6-126,3:	STRING	"uR'''spam\n'''"
+125,6-126,3:	STRING	"bR'''spam\n'''"
 126,3-126,4:	NEWLINE	'\n'
 127,0-127,1:	NL	'\n'
 128,0-128,13:	COMMENT	'# Indentation'