use assert[Not]In where appropriate
diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
index 16e65ca..553eacf 100644
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -1405,7 +1405,7 @@
                 Subclass(newarg=1)
             except TypeError as err:
                 # we expect type errors because of wrong argument count
-                self.assertFalse("does not take keyword arguments" in err.args[0])
+                self.assertNotIn("does not take keyword arguments", err.args[0])
 
 
 libreftest = """ Doctest for examples in the library reference: libitertools.tex