docs: fix two warnings in the release-notes process

... and change "tox doc" to fail next time this happens.

Author: nedbat

Makefile

@@ -166,7 +166,7 @@ RELNOTES_JSON = tmp/relnotes.json
 
 $(CHANGES_MD): CHANGES.rst $(DOCBIN)
 	$(SPHINXBUILD) -b rst doc tmp/rst_rst
-	pandoc -frst -tmarkdown_strict --atx-headers --wrap=none tmp/rst_rst/changes.rst > $(CHANGES_MD)
+	pandoc -frst -tmarkdown_strict --markdown-headings=atx --wrap=none tmp/rst_rst/changes.rst > $(CHANGES_MD)
 
 relnotes_json: $(RELNOTES_JSON)		## Convert changelog to JSON for further parsing.
 $(RELNOTES_JSON): $(CHANGES_MD)

doc/changes.rst

@@ -379,7 +379,7 @@ Version 5.0a6 — 2019-07-16
     so should only be used between two installations of the same version of
     coverage.py.
 
-  - The :meth:`CoverageData constructor<.CoverageData.__init__>` has a new
+  - The :class:`CoverageData constructor<.CoverageData>` has a new
     argument, `no_disk` (default: False).  Setting it to True prevents writing
     any data to the disk.  This is useful for transient data objects.
 

tox.ini

@@ -64,7 +64,7 @@ commands =
     make cmd_help
     python doc/check_copied_from.py doc/*.rst
     doc8 -q --ignore-path 'doc/_*' doc CHANGES.rst README.rst
-    sphinx-build -b html -aqE doc doc/_build/html
+    sphinx-build -b html -aEnqW doc doc/_build/html
     rst2html.py --strict README.rst doc/_build/trash
     - sphinx-build -b html -b linkcheck -aEnq doc doc/_build/html
     - sphinx-build -b html -b linkcheck -aEnQW doc doc/_build/html