Comment 7 for bug 1378270

I was having the same issue on Ubuntu 14.04 with the latest updates. I had version 1.5.2 installed, but using pip to try to upgrade it didn't work.

$ python -c "import six; print(six.__version__)"
1.5.2

I figured out exactly where it was being pulled from and deleted it.

$ python -v -c "import six; print(six.__version__)"
...
import six # from /usr/lib/python2.7/dist-packages/six.py
...
$ sudo rm -f /usr/lib/python2.7/dist-packages/six.py /usr/lib/python2.7/dist-packages/six.pyc

Python then used 1.8.0 from a different location (from /usr/local/lib instead of /usr/lib):

$ python -c "import six; print(six.__version__)"
1.8.0
$ python -v -c "import six; print(six.__version__)"
...
import six # precompiled from /usr/local/lib/python2.7/dist-packages/six.pyc
...