I can no longer reproduce this issue. Has it been fixed?

$ make html
mkdir -p build
Building NEWS from Misc/NEWS.d with blurb
PATH=./venv/bin:$PATH sphinx-build -b html -d build/doctrees   -W . build/html 
Running Sphinx v2.2.0
making output directory... done
building [mo]: targets for 0 po files that are out of date
building [html]: targets for 486 source files that are out of date
updating environment: [new config] 486 added, 0 changed, 0 removed
/home/epicfaace/cpython/Doc/venv/lib/python3.6/site-packages/sphinx/util/nodes.py:151: FutureWarning:              
   The iterable returned by Node.traverse()
   will become an iterator instead of a list in Docutils > 0.16.
  for classifier in reversed(node.parent.traverse(nodes.classifier)):
reading sources... [100%] whatsnew/index                                                                           
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
writing output... [100%] whatsnew/index                                                                            
generating indices...  genindex py-modindexdone
writing additional pages...  download index search opensearchdone
copying images... [100%] using/win_installer.png                                                                   
copying downloadable files... [100%] includes/tzinfo_examples.py                                                   
copying static files... ... done
copying extra files... done
dumping search index in English (code: en)... done
dumping object inventory... done
build succeeded.

The HTML pages are in build/html.

Build finished. The HTML pages are in build/html.