Require six>=1.9 for Python.
We use six sub-modules that aren't available in old versions. Not specifying
this requirement in the setup will lead to much less readable runtime errors.
It's particuarlly problematic for Mac OSX users because the system comes with
an old six version 1.4.1 by default.
[skip ci]
diff --git a/python/tox.ini b/python/tox.ini
index 3ca3934..301335b 100644
--- a/python/tox.ini
+++ b/python/tox.ini
@@ -21,6 +21,6 @@
# cpp: python setup.py -q test_conformance --cpp_implementation
deps =
# Keep this list of dependencies in sync with setup.py.
- six
+ six>=1.9
py26: ordereddict
py26: unittest2
