add posargs to pep8

we want to be able to specify --output-file

Change-Id: Ifcf158bc928ea2513a247f38622f303bee749889

tox.ini

diff --git a/tox.ini b/tox.ini
index d2f044f..d3ef981 100644
--- a/tox.ini
+++ b/tox.ini
@@ -31,4 +31,4 @@
       pydocstyle<4.0.0
       # used by flake8-rst-docstrings
       pygments
-commands = flake8 ./mako/ ./test/ setup.py --exclude test/templates,test/foo
+commands = flake8 ./mako/ ./test/ setup.py --exclude test/templates,test/foo  {posargs}