Add pyflakes to tox.ini

Add the ability to use pyflakes.

Change-Id: I1c0a652258fd494bf6754b5b83c47166582a85d0
Signed-off-by: Chuck Short <chuck.short@canonical.com>

tools/flakes.py

@@ -0,0 +1,22 @@
+"""
+ wrapper for pyflakes to ignore gettext based warning:
+     "undefined name '_'"
+
+ From https://bugs.launchpad.net/pyflakes/+bug/844592
+"""
+import __builtin__
+import os
+import sys
+
+from pyflakes.scripts.pyflakes import main
+
+if __name__ == "__main__":
+    names = os.environ.get('PYFLAKES_BUILTINS', '_')
+    names = [x.strip() for x in names.split(',')]
+    for x in names:
+        if not hasattr(__builtin__, x):
+            setattr(__builtin__, x, True)
+
+    del names, os, __builtin__
+
+    sys.exit(main())

tox.ini

@@ -27,3 +27,7 @@ setenv = NOSE_WITH_COVERAGE=1
 
 [testenv:venv]
 commands = {posargs}
+
+[testenv:pyflakes]
+deps = pyflakes
+commands = python tools/flakes.py keystone