=== modified file 'debian/rules'
--- debian/rules	2014-08-06 05:50:43 +0000
+++ debian/rules	2017-03-04 20:06:07 +0000
@@ -12,7 +12,7 @@
 	rm -rf build
 
 override_dh_auto_build:
-	sphinx-build -b html -W  docs/ docs/_build/html/
+	sphinx-build -b html docs/ docs/_build/html/
 	dh_auto_build
 
 override_dh_auto_test:

=== modified file 'docs/conf.py'
--- docs/conf.py	2013-10-14 21:01:33 +0000
+++ docs/conf.py	2017-03-04 20:06:07 +0000
@@ -46,7 +46,7 @@
 extensions = [
     'sphinx.ext.autodoc',
     'sphinx.ext.graphviz',
-    'sphinx.ext.pngmath',
+    'sphinx.ext.imgmath',
     'sphinx.ext.viewcode',
     'otto',
 ]

=== modified file 'docs/otto.py'
--- docs/otto.py	2013-07-25 05:47:36 +0000
+++ docs/otto.py	2017-03-04 20:06:07 +0000
@@ -56,12 +56,9 @@
                              self.content, self.lineno, self.content_offset,
                              self.block_text, self.state, self.state_machine)
         image_container = nodes.container()
-        image_container.children.append(nodes.image(uri='/images/otto-64.png'))
+        image_container.append(nodes.image(uri='/images/otto-64.png'))
         image_container['classes'] = ['otto-image-container']
         outer_container = nodes.container()
-        outer_container.children.extend(
-            [image_container]
-            + ad
-        )
+        outer_container.extend([image_container] + ad)
         outer_container['classes'] = ['otto-says-container']
         return [outer_container]