per feedback from @ejucovy, warn about shadowing gettext with "_"

docs/conf.py

@@ -25,7 +25,7 @@ sys.path.append(os.path.abspath('_themes'))
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.ifconfig', 'sphinx.ext.todo']
+extensions = ['sphinx.ext.ifconfig', 'sphinx.ext.todo', 'sphinx.ext.intersphinx']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
@@ -260,3 +260,7 @@ epub_copyright = u'2010, Kenneth Reitz'
 #epub_tocdup = True
 
 todo_include_todos = True
+
+intersphinx_mapping = {
+    'python': ('http://docs.python.org/', None),
+}