Pass posargs to 'docs' target

This lets us pass things like '-E' (to discard environment) when needed.

Signed-off-by: Stephen Finucane <[email protected]>

Author: stephenfin

tox.ini

@@ -22,7 +22,7 @@ description = invoke sphinx-build to build the HTML docs and check that all link
 whitelist_externals = sphinx-build
 basepython = python3.6
 extras = docs
-commands = sphinx-build -d "{toxworkdir}/docs_doctree" doc "{toxworkdir}/docs_out" --color -W -bhtml
+commands = sphinx-build -d "{toxworkdir}/docs_doctree" doc "{toxworkdir}/docs_out" --color -W -bhtml {posargs}
 
 
 [testenv:fix-lint]