Make binascii use byte strings everywhere (in and out).
diff --git a/Lib/test/test_binascii.py b/Lib/test/test_binascii.py
index a4ee7f8..d1a4cfb 100755
--- a/Lib/test/test_binascii.py
+++ b/Lib/test/test_binascii.py
@@ -7,10 +7,10 @@
 class BinASCIITest(unittest.TestCase):
 
     # Create binary test data
-    data = "The quick brown fox jumps over the lazy dog.\r\n"
+    data = b"The quick brown fox jumps over the lazy dog.\r\n"
     # Be slow so we don't depend on other modules
-    data += "".join(map(chr, range(256)))
-    data += "\r\nHello world.\n"
+    data += bytes(range(256))
+    data += b"\r\nHello world.\n"
 
     def test_exceptions(self):
         # Check module exceptions
@@ -40,10 +40,10 @@
             b = self.data[i:i+MAX_BASE64]
             a = binascii.b2a_base64(b)
             lines.append(a)
-        res = ""
+        res = bytes()
         for line in lines:
             b = binascii.a2b_base64(line)
-            res = res + b
+            res += b
         self.assertEqual(res, self.data)
 
     def test_base64invalid(self):
@@ -56,24 +56,23 @@
             a = binascii.b2a_base64(b)
             lines.append(a)
 
-        fillers = ""
-        valid = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+/"
+        fillers = bytes()
+        valid = b"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+/"
         for i in range(256):
-            c = chr(i)
-            if c not in valid:
-                fillers += c
+            if i not in valid:
+                fillers.append(i)
         def addnoise(line):
             noise = fillers
             ratio = len(line) // len(noise)
-            res = ""
+            res = bytes()
             while line and noise:
                 if len(line) // len(noise) > ratio:
                     c, line = line[0], line[1:]
                 else:
                     c, noise = noise[0], noise[1:]
-                res += c
+                res.append(c)
             return res + noise + line
-        res = ""
+        res = bytes()
         for line in map(addnoise, lines):
             b = binascii.a2b_base64(line)
             res += b
@@ -81,7 +80,7 @@
 
         # Test base64 with just invalid characters, which should return
         # empty strings. TBD: shouldn't it raise an exception instead ?
-        self.assertEqual(binascii.a2b_base64(fillers), '')
+        self.assertEqual(binascii.a2b_base64(fillers), b'')
 
     def test_uu(self):
         MAX_UU = 45
@@ -90,23 +89,23 @@
             b = self.data[i:i+MAX_UU]
             a = binascii.b2a_uu(b)
             lines.append(a)
-        res = ""
+        res = bytes()
         for line in lines:
             b = binascii.a2b_uu(line)
             res += b
         self.assertEqual(res, self.data)
 
-        self.assertEqual(binascii.a2b_uu("\x7f"), "\x00"*31)
-        self.assertEqual(binascii.a2b_uu("\x80"), "\x00"*32)
-        self.assertEqual(binascii.a2b_uu("\xff"), "\x00"*31)
-        self.assertRaises(binascii.Error, binascii.a2b_uu, "\xff\x00")
-        self.assertRaises(binascii.Error, binascii.a2b_uu, "!!!!")
+        self.assertEqual(binascii.a2b_uu(b"\x7f"), b"\x00"*31)
+        self.assertEqual(binascii.a2b_uu(b"\x80"), b"\x00"*32)
+        self.assertEqual(binascii.a2b_uu(b"\xff"), b"\x00"*31)
+        self.assertRaises(binascii.Error, binascii.a2b_uu, b"\xff\x00")
+        self.assertRaises(binascii.Error, binascii.a2b_uu, b"!!!!")
 
-        self.assertRaises(binascii.Error, binascii.b2a_uu, 46*"!")
+        self.assertRaises(binascii.Error, binascii.b2a_uu, 46*b"!")
 
     def test_crc32(self):
-        crc = binascii.crc32("Test the CRC-32 of")
-        crc = binascii.crc32(" this string.", crc)
+        crc = binascii.crc32(b"Test the CRC-32 of")
+        crc = binascii.crc32(b" this string.", crc)
         self.assertEqual(crc, 1571220330)
 
         self.assertRaises(TypeError, binascii.crc32)
@@ -115,16 +114,16 @@
 
     def test_hex(self):
         # test hexlification
-        s = '{s\005\000\000\000worldi\002\000\000\000s\005\000\000\000helloi\001\000\000\0000'
+        s = b'{s\005\000\000\000worldi\002\000\000\000s\005\000\000\000helloi\001\000\000\0000'
         t = binascii.b2a_hex(s)
         u = binascii.a2b_hex(t)
         self.assertEqual(s, u)
         self.assertRaises(TypeError, binascii.a2b_hex, t[:-1])
-        self.assertRaises(TypeError, binascii.a2b_hex, t[:-1] + 'q')
+        self.assertRaises(TypeError, binascii.a2b_hex, t[:-1] + b'q')
 
         # Verify the treatment of Unicode strings
         if test_support.have_unicode:
-            self.assertEqual(binascii.hexlify(str('a', 'ascii')), '61')
+            self.assertEqual(binascii.hexlify('a'), b'61')
 
     def test_qp(self):
         # A test for SF bug 534347 (segfaults without the proper fix)
@@ -134,28 +133,29 @@
             pass
         else:
             self.fail("binascii.a2b_qp(**{1:1}) didn't raise TypeError")
-        self.assertEqual(binascii.a2b_qp("= "), "= ")
-        self.assertEqual(binascii.a2b_qp("=="), "=")
-        self.assertEqual(binascii.a2b_qp("=AX"), "=AX")
+        self.assertEqual(binascii.a2b_qp(b"= "), b"= ")
+        self.assertEqual(binascii.a2b_qp(b"=="), b"=")
+        self.assertEqual(binascii.a2b_qp(b"=AX"), b"=AX")
         self.assertRaises(TypeError, binascii.b2a_qp, foo="bar")
-        self.assertEqual(binascii.a2b_qp("=00\r\n=00"), "\x00\r\n\x00")
+        self.assertEqual(binascii.a2b_qp(b"=00\r\n=00"), b"\x00\r\n\x00")
         self.assertEqual(
-            binascii.b2a_qp("\xff\r\n\xff\n\xff"),
-            "=FF\r\n=FF\r\n=FF"
+            binascii.b2a_qp(b"\xff\r\n\xff\n\xff"),
+            b"=FF\r\n=FF\r\n=FF"
         )
         self.assertEqual(
-            binascii.b2a_qp("0"*75+"\xff\r\n\xff\r\n\xff"),
-            "0"*75+"=\r\n=FF\r\n=FF\r\n=FF"
+            binascii.b2a_qp(b"0"*75+b"\xff\r\n\xff\r\n\xff"),
+            b"0"*75+b"=\r\n=FF\r\n=FF\r\n=FF"
         )
 
-        self.assertEqual(binascii.b2a_qp('\0\n'), '=00\n')
-        self.assertEqual(binascii.b2a_qp('\0\n', quotetabs=True), '=00\n')
-        self.assertEqual(binascii.b2a_qp('foo\tbar\t\n'), 'foo\tbar=09\n')
-        self.assertEqual(binascii.b2a_qp('foo\tbar\t\n', quotetabs=True), 'foo=09bar=09\n')
+        self.assertEqual(binascii.b2a_qp(b'\0\n'), b'=00\n')
+        self.assertEqual(binascii.b2a_qp(b'\0\n', quotetabs=True), b'=00\n')
+        self.assertEqual(binascii.b2a_qp(b'foo\tbar\t\n'), b'foo\tbar=09\n')
+        self.assertEqual(binascii.b2a_qp(b'foo\tbar\t\n', quotetabs=True),
+                         b'foo=09bar=09\n')
 
-        self.assertEqual(binascii.b2a_qp('.'), '=2E')
-        self.assertEqual(binascii.b2a_qp('.\n'), '=2E\n')
-        self.assertEqual(binascii.b2a_qp('a.\n'), 'a.\n')
+        self.assertEqual(binascii.b2a_qp(b'.'), b'=2E')
+        self.assertEqual(binascii.b2a_qp(b'.\n'), b'=2E\n')
+        self.assertEqual(binascii.b2a_qp(b'a.\n'), b'a.\n')
 
     def test_empty_string(self):
         # A test for SF bug #1022953.  Make sure SystemError is not raised.
@@ -164,7 +164,10 @@
                   'a2b_hqx', 'a2b_base64', 'rlecode_hqx', 'b2a_uu',
                   'rledecode_hqx']:
             f = getattr(binascii, n)
-            f('')
+            try:
+                f(b'')
+            except SystemError as err:
+                self.fail("%s(b'') raises SystemError: %s" % (n, err))
         binascii.crc_hqx('', 0)
 
 def test_main():