add nocmk tox testenv to verify that local tests run successfully with no environment variables set

Author: mattsb42-aws

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    py{27,34,35,36}-{local,integ}-fast,
+    py{27,34,35,36}-{local,integ}-fast, nocmk,
     bandit, doc8, readme,
     flake8, pylint,
     flake8-tests, pylint-tests,
@@ -44,6 +44,13 @@ commands =
     # Do not select any specific markers
     manual: {[testenv:base-command]commands}
 
+# Verify that local tests work without environment variables present
+[testenv:nocmk]
+basepython = python3
+sitepackages = False
+deps = -rtest/requirements.txt
+commands = {[testenv:base-command]commands} -m "local and not slow and not veryslow and not nope"
+
 # mypy
 [testenv:mypy-coverage]
 commands =