Update test for displaying subclass instance

IPython/core/tests/test_formatters.py

@@ -49,7 +49,7 b' def test_pretty():'
     f = PlainTextFormatter()
     f.for_type(A, foo_printer)
     nt.assert_equal(f(A()), 'foo')
-    nt.assert_equal(f(B()), 'foo')
+    nt.assert_equal(f(B()), 'B()')
     nt.assert_equal(f(GoodPretty()), 'foo')
     # Just don't raise an exception for the following:
     f(BadPretty())