install argparse for 2.6

closes #2476

tox.ini

@@ -59,13 +59,8 @@ passenv = CI TRAVIS TRAVIS_*
 deps = codecov
 skip_install = true
 commands =
+    # install argparse for 2.6
+    python -c 'import sys, pip; sys.version_info < (2, 7) and pip.main(["install", "argparse", "-q"])'
     coverage combine
     coverage report
     codecov
-
-[testenv:detox]
-skip_install = true
-deps = detox
-commands =
-    detox -e py{36,35,34,33,27,26,py},py{36,27,py}-simplejson,py{36,33,27,26,py}-devel,py{36,33,27,26,py}-lowest
-    tox -e docs-html,coverage-report