I encountered the same ImportError. Somehow the setuptools package had been deleted in my Python environment.
To fix the issue, run the setup script for setuptools:
curl https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py | python
If you have any version of distribute, or any setuptools below 0.6, you will have to uninstall it first.*
See Installation Instructions for further details.
* If you already have a working distribute, upgrading it to the “compatibility wrapper” that switches you over to setuptools is easier. But if things are already broken, don’t try that.