Add restructuredtext_lint to test (#1598)

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

.travis.yml

@@ -20,6 +20,10 @@ matrix:
       env: TOXENV=py38-dev
       dist: xenial
       sudo: true
+    - python: 3.7
+      env: TOXENV=docs-lint
+      dist: xenial
+      sudo: true
   allow_failures:
     - env: TOXENV=py38-dev
 install: pip install tox

tox.ini

@@ -27,3 +27,15 @@ commands =
     tests/test_valid_requests.py
 deps =
   pylint
+
+[testenv:docs-lint]
+whitelist_externals =
+  rst-lint
+  bash
+  grep
+deps =
+  restructuredtext_lint
+  pygments
+commands =
+  rst-lint README.rst docs/README.rst
+  bash -c "(set -o pipefail; rst-lint --encoding utf-8 docs/source/*.rst | grep -v 'Unknown interpreted text role\|Unknown directive type'); test $? == 1"