Issues with pip, pbr, and setuptools

Donald Stufft summarized this very well:

pip 1.5.x installs wheels by default, they are a new packaging format, and they use a .dist-info directory as it's meta directory, setuptools doesn't recognize the .dist-info directory until 0.6.28, so setuptools doesn't see the fact that pip has installed six, because it's installed with the dist-info dir. so basically you just need to either ensure that your setuptools is 0.6.28+ (doable inside of a virtual environment as you noted), or use --no-use-wheel when using pip 1.5.x

So if you are having issues, please try one of the above solutions.