re-enable the interpretation of the None keyword

test/completion/stdlib.py

@@ -18,7 +18,7 @@ next(reversed(arr))
 def yielder():
     yield None
 
-#?
+#? None
 next(reversed(yielder()))
 
 # empty reversed should not raise an error

test/test_api/test_full_name.py

@@ -15,6 +15,8 @@ There are three kinds of test:
 
 import textwrap
 
+import pytest
+
 import jedi
 from jedi.api import classes
 from jedi.evaluate import Evaluator
@@ -42,6 +44,7 @@ class MixinTestFullName(object):
 class TestFullNameWithGotoDefinitions(MixinTestFullName, TestCase):
     operation = 'goto_definitions'
 
+    @pytest.mark.skipif('sys.version_info[:2] <= (2, 6)', reason='Python 2.6 also yields None.')
     def test_tuple_mapping(self):
         self.check("""
         import re