Merge "Update min version of tox"

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-minversion = 2.0
+minversion = 3.18.0
 envlist = pep8,docs
 skipsdist = True
 
@@ -16,7 +16,7 @@ commands = {posargs}
 
 [testenv:docs]
 deps = -r{toxinidir}/doc/requirements.txt
-whitelist_externals = rm
+allowlist_externals = rm
 commands =
   rm -fr doc/build
   sphinx-build -W -b html doc/source doc/build/html