Skip readline tests if readline module is not available.

Lib/test/test_readline.py

@@ -6,9 +6,10 @@ the "real" readline have the same interface for history manipulation. That's
 why the tests cover only a small subset of the interface.
 """
 import unittest
-from test.test_support import run_unittest
+from test.test_support import run_unittest, import_module
 
-import readline
+# Skip tests if there is no readline module
+readline = import_module('readline')
 
 class TestHistoryManipulation (unittest.TestCase):
     def testHistoryUpdates(self):