code: def find_pth_directory():
      
      return ('/' if 'bdist_wheel' in sys.argv
              else os.path.relpath(distutils.sysconfig.get_python_lib(), sys.prefix))
docs: Determine the correct directory pathname for installing ``*.pth`` files.
  
      To install a ``*.pth`` file using a source distribution archive (created
      when ``python setup.py sdist`` is called) the relative directory pathname
      ``lib/pythonX.Y/site-packages`` needs to be passed to the ``data_files``
      option to ``setup()``.
  
      Unfortunately this breaks universal wheel archives (created when ``python
      setup.py bdist_wheel --universal`` is called) because a specific Python
      version is now encoded in the pathname of a directory that becomes part of
      the supposedly universal archive :-).
  
      Through trial and error I've found that by passing the directory pathname
      ``/`` when ``python setup.py bdist_wheel`` is called we can ensure that
      ``*.pth`` files are installed in the ``lib/pythonX.Y/site-packages``
      directory without hard coding its location.