use assert[Not]IsInstance where appropriate
diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
index 27ed92e..1d7fd73 100644
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -66,8 +66,7 @@
 
     def test_fileno(self):
         file_num = self.returned_obj.fileno()
-        self.assertTrue(isinstance(file_num, int),
-                     "fileno() did not return an int")
+        self.assertIsInstance(file_num, int, "fileno() did not return an int")
         self.assertEqual(os.read(file_num, len(self.text)), self.text,
                          "Reading on the file descriptor returned by fileno() "
                          "did not return the expected text")
@@ -78,7 +77,7 @@
         self.returned_obj.close()
 
     def test_info(self):
-        self.assertTrue(isinstance(self.returned_obj.info(), mimetools.Message))
+        self.assertIsInstance(self.returned_obj.info(), mimetools.Message)
 
     def test_geturl(self):
         self.assertEqual(self.returned_obj.geturl(), self.pathname)
@@ -229,9 +228,9 @@
         # a headers value is returned.
         result = urllib.urlretrieve("file:%s" % test_support.TESTFN)
         self.assertEqual(result[0], test_support.TESTFN)
-        self.assertTrue(isinstance(result[1], mimetools.Message),
-                     "did not get a mimetools.Message instance as second "
-                     "returned value")
+        self.assertIsInstance(result[1], mimetools.Message,
+                              "did not get a mimetools.Message instance as "
+                              "second returned value")
 
     def test_copy(self):
         # Test that setting the filename argument works.
@@ -254,9 +253,9 @@
     def test_reporthook(self):
         # Make sure that the reporthook works.
         def hooktester(count, block_size, total_size, count_holder=[0]):
-            self.assertTrue(isinstance(count, int))
-            self.assertTrue(isinstance(block_size, int))
-            self.assertTrue(isinstance(total_size, int))
+            self.assertIsInstance(count, int)
+            self.assertIsInstance(block_size, int)
+            self.assertIsInstance(total_size, int)
             self.assertEqual(count, count_holder[0])
             count_holder[0] = count_holder[0] + 1
         second_temp = "%s.2" % test_support.TESTFN