--- a/doc/models/source/conf.py	Mon Jan 07 17:29:27 2019 -0800
+++ b/doc/models/source/conf.py	Mon Jan 07 21:22:23 2019 -0800
@@ -25,7 +25,7 @@
 
 # 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.pngmath']
+extensions = ['sphinx.ext.imgmath']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']

--- a/doc/tutorial-pt-br/source/conf.py	Mon Jan 07 17:29:27 2019 -0800
+++ b/doc/tutorial-pt-br/source/conf.py	Mon Jan 07 21:22:23 2019 -0800
@@ -25,7 +25,7 @@
 
 # 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.pngmath']
+extensions = ['sphinx.ext.imgmath']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']

--- a/doc/tutorial/source/conf.py	Mon Jan 07 17:29:27 2019 -0800
+++ b/doc/tutorial/source/conf.py	Mon Jan 07 21:22:23 2019 -0800
@@ -25,7 +25,7 @@
 
 # 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.pngmath']
+extensions = ['sphinx.ext.imgmath']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']