title: Error: setup script specifies an absolute path: .gitignore
body: <p>On Ubuntu 16.04.4, I suspect some recent update of some Python system package of having broken my Python 2.7 configuration. Whatever package I try to install or reinstall with a basic <code>sudo python setup.py install</code> it always fails because of gitignore:</p>
  
  <pre><code>running install
  running bdist_egg
  running egg_info
  [...]
  installing library code to build/bdist.linux-x86_64/egg
  running install_lib
  running build_py
  
  error: Error: setup script specifies an absolute path:
  
      /home/me/some_repo/.gitignore
  
  setup() arguments must *always* be /-separated paths relative to the
  setup.py directory, *never* absolute paths.
  </code></pre>
  
  <p>Lately I found a temporary workaround by manually cleaning the <code>/usr/local/lib/python2.7/dist-packages/some_package</code> directory manually before installing <code>some_package</code>. However tonight I'm facing the same issue on another repository and it keeps failing whatever I clean up. I also tried cleaning all compiled folders <code>.egg-info/ build/ dist/</code> without success.</p>
  
  <p>Notes: The setup script does not actually specify an absolute path to gitignore. An example of failing repo is <a href="https://github.com/philchristensen/python-artnet/blob/master/setup.py" rel="nofollow noreferrer">https://github.com/philchristensen/python-artnet/blob/master/setup.py</a> This repo has a setuptools_git entry which might lead to a clue, but other packages without this git entry point also fail because of the gitignore while a couple of months ago I never faced such issue with the same repos. Deleting the gitignore causes the setup to fail because of another non-py local file.</p>
  
  <p>Any clue?</p>