Released v6.0.7

* Fix a regression where Numpy requires a build path without symlinks to
  properly build.

* Fix a broken log message when running ``pip wheel`` without a requirement.

* Don't mask network errors while downloading the file as a hash failure.

* Properly create the state file for the pip version check so it only happens
  once a week.

* Fix an issue where switching between Python 3 and Python 2 would evict cached
  items.

* Fix a regression where pip would be unable to successfully uninstall a
  project without a normalized version.