Merge pull request #470 from adamtheturtle/pyup-update-sphinx-2.3.0-to-2.3.1

Update sphinx to 2.3.1

Author: adamtheturtle

dev-requirements.txt

@@ -1,6 +1,6 @@
 PyYAML==5.2
 Sphinx-Substitution-Extensions==2019.6.15.0
-Sphinx==2.3.0
+Sphinx==2.3.1
 VWS-Auth-Tools==2019.12.8.2
 VWS-Test-Fixtures==2019.12.13.1
 attrs==19.3.0  # Modern attrs is required for pytest