use assert[Not]IsInstance where appropriate
diff --git a/Lib/test/test_zipfile.py b/Lib/test/test_zipfile.py
index cd954f9..2c7d330 100644
--- a/Lib/test/test_zipfile.py
+++ b/Lib/test/test_zipfile.py
@@ -593,7 +593,7 @@
         with zipfile.ZipFile(TESTFN, "w") as zf:
             zf.writestr(u"foo.txt", "Test for unicode filename")
             zf.writestr(u"\xf6.txt", "Test for unicode filename")
-            self.assertTrue(isinstance(zf.infolist()[0].filename, unicode))
+            self.assertIsInstance(zf.infolist()[0].filename, unicode)
 
         with zipfile.ZipFile(TESTFN, "r") as zf:
             self.assertEqual(zf.filelist[0].filename, "foo.txt")