Remove deprecated Sphinx directive add_description_unit() (#714)

mikedep333 · blueyed · commit 5c91295c5818 · 2019-04-01T19:14:07.000+02:00
Sphinx 2.0 dropped support for it. See pytest-dev/pytest#4922
diff --git a/docs/conf.py b/docs/conf.py
@@ -50,7 +50,7 @@
 
 def setup(app):
     # Allow linking to pytest's confvals.
-    app.add_description_unit(
+    app.add_object_type(
         "confval",
         "pytest-confval",
         objname="configuration value",
