Adding intersphinx for docs linking.

Author: dhermes

docs/conf.py

@@ -39,6 +39,7 @@
     'sphinx.ext.autodoc',
     'sphinx.ext.autosummary',
     'sphinx.ext.doctest',
+    'sphinx.ext.intersphinx',
     'sphinx.ext.todo',
     'sphinx.ext.viewcode',
 ]
@@ -284,3 +285,13 @@
     issue_uri=issue_uri,
     issue_uri_template=issue_uri_template,
 )
+
+# Configuration for intersphinx:
+# Refer to the Python standard library and oauth2client library.
+# NOTE: We also have a custom mapping for items in the stdlib not
+#       included in https://docs.python.org/objects.inv
+intersphinx_mapping = {
+    'python': ('https://docs.python.org/', None),
+    'pythonlocal': ('https://docs.python.org/2.7/', 'python-inv.txt'),
+    'oauth2client': ('http://google.github.io/oauth2client/', None),
+}

docs/python-inv.txt

@@ -0,0 +1,12 @@
+# Sphinx inventory version 1
+# Project: Python
+# Version: 2.7
+types mod library/types.html
+types.NoneType data library/types.html
+types.NoneType class library/types.html
+True data library/constants.html
+False data library/constants.html
+None data library/constants.html
+exceptions mod library/exceptions.html
+exceptions.ValueError exception library/exceptions.html
+exceptions.TypeError exception library/exceptions.html