Build the documentation in Travis CI and fail on documentation issues (#86)

Author: Gallaecio

.travis.yml

@@ -9,6 +9,8 @@ matrix:
       env: TOXENV=py35,stack-scrapy-1.1-py3,stack-scrapy-1.2-py3
     - python: 3.6
       env: TOXENV=py36,stack-scrapy-1.3-py3,stack-scrapy-1.4-py3,stack-scrapy-1.5-py3
+    - python: 3.8
+      env: TOXENV=docs
 
 install:
     - pip install -U tox codecov

tox.ini

@@ -131,4 +131,4 @@ deps =
 changedir = {[docs]changedir}
 deps = {[docs]deps}
 commands =
-    sphinx-build -W -b html . {envtmpdir}/html
+    sphinx-build -nW -b html . {envtmpdir}/html