switch to twine check for verifying our readme renders on pypi (#4623)

diff --git a/setup.py b/setup.py
index 886d932..937d1ac 100644
--- a/setup.py
+++ b/setup.py
@@ -303,7 +303,7 @@
         "docstest": [
             "doc8",
             "pyenchant >= 1.6.11",
-            "readme_renderer >= 16.0",
+            "twine >= 1.12.0",
             "sphinxcontrib-spelling >= 4.0.1",
         ],
         "pep8test": [
diff --git a/tox.ini b/tox.ini
index 7e6b56c..f6e1b6e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -46,7 +46,8 @@
     sphinx-build -j4 -T -W -b doctest -d {envtmpdir}/doctrees docs docs/_build/html
     sphinx-build -j4 -T -W -b spelling docs docs/_build/html
     doc8 --allow-long-titles README.rst CHANGELOG.rst docs/ --ignore-path docs/_build/
-    python setup.py check --restructuredtext --strict
+    python setup.py sdist
+    twine check dist/*
 
 [testenv:docs-linkcheck]
 extras =