[2.7] bpo-35564: add master_doc='contents' to conf.py (GH-12462)

(cherry picked from commit fc8284e2)
Co-authored-by: Jean-François B <jfbu@free.fr>

Doc/conf.py

@@ -41,6 +41,8 @@ exclude_patterns = [
 # Require Sphinx 1.2 for build.
 needs_sphinx = '1.2'
 
+# Avoid a warning with Sphinx >= 2.0
+master_doc = 'contents'
 
 # Options for HTML output
 # -----------------------

Misc/NEWS.d/next/Documentation/2018-12-22-22-52-05.bpo-35564.TuEU_D.rst

+Explicitly set master_doc variable in conf.py for compliance with Sphinx 2.0