matplotlib · NelleV · Mar 8, 2017 · Mar 7, 2017
diff --git a/doc/conf.py b/doc/conf.py
@@ -14,6 +14,7 @@
 import os
 import sys
 import sphinx
+import six

 # If your extensions are in another directory, add it here. If the directory
 # is relative to the documentation root, use os.path.abspath to make it
@@ -73,6 +74,16 @@
    raise ImportError("No module named Image - you need to install "
                      "pillow to build the documentation")

+if six.PY2:
+    from distutils.spawn import find_executable
+    has_dot = find_executable('dot') is not None
+else:
+    from shutil import which  # Python >= 3.3
+    has_dot = which('dot') is not None
+if not has_dot:
+    raise OSError(
+        "No binary named dot - you need to install the Graph Visualization "
+        "software (usually packaged as 'graphviz') to build the documentation")

 try:
    import matplotlib