Comment 1 for bug 725178

Pip uninstall calls the Distribution.egg_name() method, and appends ".egg-info", to determine where to find package metadata. This is precisely the same technique used by setuptools/distribute's install_egg_info command to determine the name of the metadata directory when creating it (see https://bitbucket.org/tarek/distribute/src/f64c2d57df43/setuptools/command/install_egg_info.py). So somehow Ubuntu's packaged version of distribute (python-setuptools) is breaking this symmetry: metadata is installed under an egg-info dir lacking pyversion, but when pip calls the Distribution.egg_name() method it gets a name back that includes pyversion.

This breaks pip uninstall for all users of Ubuntu's python-setuptools package. As far as I can tell there is nothing wrong with what pip is doing here; the breakage is in Ubuntu's package.