docs: only use sphinxcontrib-doxylink on Python 3

disable sphinxcontrib-googleanalytics

refs #4553

Change-Id: I552c190e2da576f77f2a0150e47392c11ef3efce
diff --git a/docs/conf.py b/docs/conf.py
index d790ce3..d95a278 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -30,10 +30,12 @@
         sys.stderr.write("To install, use \n"
                          "  sudo pip install %s\n" % extension.replace('.', '-'))
 
-addExtensionIfExists('sphinxcontrib.doxylink')
+if sys.version_info[0] >= 3:
+    addExtensionIfExists('sphinxcontrib.doxylink')
 
-if os.getenv('GOOGLE_ANALYTICS', None):
-    addExtensionIfExists('sphinxcontrib.googleanalytics')
+# sphinxcontrib.googleanalytics is currently not working with the latest version of sphinx
+# if os.getenv('GOOGLE_ANALYTICS', None):
+#     addExtensionIfExists('sphinxcontrib.googleanalytics')
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']