Pass extra tox args to the test cli to allow running partial tests

tox.ini

@@ -18,7 +18,7 @@ setenv =
 
 commands =
     coverage erase
-    coverage run manage.py test -v 2 --exclude-tag nntp
+    coverage run manage.py test -v 2 --exclude-tag nntp {posargs}
     coverage report --include='debexpo*' --omit '*/nntp.py'
     coverage html --include='debexpo*' --omit '*/nntp.py'