tox.ini: Look for Python syntax errors and undefined names (#721)

diff --git a/tox.ini b/tox.ini
index 35cb0ea..13a718b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -14,9 +14,12 @@
        pycrypto==2.6
        django<2.0.0; python_version < '3.0.0'
        django>=2.0.0; python_version > '3.0.0'
+       flake8
        webtest
        nose
        coverage>=3.6,<3.99
        unittest2
        mock
-commands = nosetests --with-coverage --cover-package=googleapiclient --nocapture --cover-erase --cover-tests --cover-branches --cover-min-percentage=85 []
+commands =
+       flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
+       nosetests --with-coverage --cover-package=googleapiclient --nocapture --cover-erase --cover-tests --cover-branches --cover-min-percentage=85 []